I also just had this issue and managed to resolve it using the method above.

Same issue occurs for Sniper Ghost Warrior Contracts 2 (1338770)

Game does not install on BTRFS based distributions due to case mismatch of folder names in the installation depots.
Installation fails at 99% with "Disk Write Error"

Specific mismatch in:
SteamLibrary/steamapps/downloading/1338770/Localization/english_xml.pak

meanwhile the download/installation process creates:
SteamLibrary/steamapps/downloading/1338770/localization/

Difference being the capitalization of /localization/ folder.

Manually changing the capitalization to uppercase L allows the installation to complete.

Reproduction

steam content_log.txt

[xxxx-xx-xx xx:xx:xx] CGenericAsyncFileIOThread::AllocateResource() failed for CFileWriter: errno: 2, File: /run/media/system/Media/SteamLibrary/steamapps/downloading/1338770/Localization/english_xml.pak
[xxxx-xx-xx xx:xx:xx] AppID 1338770 App update changed : Running Update,Stopping,
[xxxx-xx-xx xx:xx:xx] AppID 1338770 App update changed : None
[xxxx-xx-xx xx:xx:xx] AppID 1338770 state changed : Update Required,Update Queued,Update Optional,Update Started, (Disk write failure)

Civ 5 (already flagged earlier) got the same issue and what annoys me the most is the steam support doing nothing, talking me nonsense although I am an IT support myself for 18 years and having spend more on that issue than them. That's so unbelievable.

The new incompetent answer from the so-called "Steam Support" regarding this issue:
_Thanks for the information. I understand how you feel.

The ticket was escalated to me.

I have read and understood your message.

However, as we have mentioned in your previous ticket, Fedora Linux 44 is not supported by Steam.

Most likely using an unsupported distribution will affect the activity on the Steam client.

Although you mentioned that your friend is experiencing the same issue while using Ubuntu, we still encourage you to use the supported version of Linux for Steam.

On the other hand, if the troubleshooting steps we have provided did not resolve the problem for the game installation, unfortunately, without physical or remote access to your computer we will not be able to troubleshoot this error better. This is due to variables caused by the multitude of hardware/software configurations that can be present.

At this time, we would suggest reaching out to a local PC specialist for assistance as they would be your best resource for more advanced troubleshooting.

If you have any further questions, please let us know - we will be happy to assist you.

Steam Support
John_

My answer
_I understand you're unable to help further through this channel.

To be clear: I will not be reinstalling my entire OS, all my games, and all my data on Ubuntu just to prove a point that has already been proven — my friend already did that test on Ubuntu, on his own existing installation, and got the identical error. That data point is exactly as valid as if I did it myself, and I'm not going to destroy a working system to satisfy a support script that isn't reading what's already been provided.

I also notice that none of your responses have acknowledged the GitHub issue I referenced (ValveSoftware/steam-for-linux#13406), which documents the exact same root cause — mismatched upper/lowercase folder names in a depot causing "File Not Found" disk write errors — on a completely different game. That report exists precisely because this is a client-side bug affecting multiple titles, not a per-user configuration issue.

For the record, the contradiction in your message speaks for itself: you acknowledge the issue reproduces on Ubuntu (your officially supported distribution) while still attributing it to "unsupported distribution." I've filed a technical bug report with root-cause analysis on Valve's GitHub tracker, which is the appropriate channel for this. Closing this ticket on my end.

At this point, three consecutive responses have failed to engage with a single piece of technical evidence provided — logs, error codes, independent reproduction on your own supported distribution, and a linked GitHub issue documenting the exact same root cause on another game. I'll let readers draw their own conclusions about the quality of support this represents._

The new incompetent answer from the so-called "Steam Support" regarding this issue:

Frankly, I must say I wouldn't expect Steam Support to be able to deal with an so far undocumented bug, possibly even a regression introduced through one of the newer client's versions, yet.

The new incompetent answer from the so-called "Steam Support" regarding this issue:

Frankly, I must say I wouldn't expect Steam Support to be able to deal with an so far undocumented bug, possibly even a regression introduced through one of the newer client's versions, yet.

The thing is, they don't even read all my troubleshooting, the URL of this github issue nor the Steam forum thread where at least four people reported this. I am unemployed at this time and I spent more time troubleshooting this issue without being paid for this than they considering the crap they keep answering.

They keep repeating steam for linux is supported only for ubuntu and they cannot help as I use Fedora and if they had taken the time to read, they would have seen this was not distro-dependent. I don't want to change distro just to be able to have a relevant answer from a crappy support should'n' I ?

The thing is, they don't even read all my troubleshooting, the URL of this github issue nor the Steam forum thread where at least four people reported this.

I understand but I think when the support have not been yet trained to deal with this, it's better to just admit they can't help you instead of experimentally poking around your system, following a seemingly random post on the internet, even though this is a fairly simple issue to fix.

This is rather expected when asking for help for a new, yet unaddressed issue. Granted, this surely affects non tech savvy users and they are ultimately dead in the water. Suggesting to switch to other distribution is rather destructive.

However, I would like to keep the comments clean for any new reports involving other games affected by this and this is not really relevant here.

Understood. My rant was principally motivated bu the fact that I am an Senior IT Support myself and I feel angered by this lack of professionnalism considering they have a job and not me.

However, I would like to keep the comments clean for any new reports involving other games affected by this and this is not really relevant >here.

Fair enough, I will restrain for comment not related to this bug and hope a solution emerge.

I believe this is also happening with Grand Theft Auto: San Andreas (12120). It fails partway through the download on two of my machines with a Disk Write Error on case-sensitive filesystems (ext4 and ZFS tested). I created a ZFS dataset with casesensitivity=insensitive, and the game installed correctly in that location.

As a basic sanity check, I did download the game on a Windows 10 machine and it downloads/installs correctly.

Same issue with a DLC for Rift of Necrodancer.

To anybody experiencing that, after locating the path in ~/.steam/debian-installation/logs/content_log.txt and doing

cd ~/.steam/debian-installation/steamapps/downloading/2073250
ln -s RiftOfTheNecroDancer_Data RiftOfTheNecrodancer_Data

download resumed, succeeded and game works. Probably similar steps can work for other games.

The beta client should have a fix for this issue. Let me know if it fixes the problem for you.

San Andreas (12120) now installs and runs on a case-sensitive filesystem when using the beta client.

The beta client should have a fix for this issue. Let me know if it fixes the problem for you.

I can confirm, Dawn of War: Dark Crusade (4580) and Civilization V (8930) now downloads with no issues on the Beta client.

The issue may be resolved in Beta but not on the stable client Steam Version: 1784778118.

I don't want to use the beta version for obvious reasons, so when the issue will be solved on it ?

The issue may be resolved in Beta but not on the stable client Steam Version: 1784778118.

Realistically, what you can do is either:

1. opt in for beta for the duration of the download and revert back,
2. manually attend the installation as listed in my post,

until the changes get pushed into stable release. Unless you have a very specific issue, there is really no risk by using the beta.

Chiming in here for same error in Sniper Elite 5 on Steam OS PC and Fedora. No errors in windows.
As others mention, opt in for beta fixed the issue for me.

I have the same issue for Grand Theft Auto San Andreas as well (12120).

Going to steamapps/downloading/12120/audio and running ln -rsv ./sfx ./SFX fixed it for me.