Hello @MartinX3, you might be seeing the issue being tracked at #7372. Can you clarify if "hangs" means that the Steam client is completely non-interactive? Also, can you try to get the thread name as described at https://github.com/ValveSoftware/steam-for-linux/issues/7372#issuecomment-696193644?
It sadly doesn't happen all the time
I think I observed it now 2 times, since I installed 5.13
The steam clients seems to act normal, just this process uses so much cpu sometimes.
(No downloads)
Now it happened again
I think with the proton update and after a restart.

Then closing steam and starting it another time fixed it.
And it happens again.
After a proton update.
I am also having this issue. I noticed it first today just after updating Proton to 5.13, but I can not say for certain that it has not been there before, but it is quite suspicious that I notice it ~5 Minutes after installing Proton 5.13 (see screenshot).
My specs:
OS: Manjaro 20.2 Nibia
Kernel: x86_64 Linux 5.8.18-1-MANJARO
Uptime: 38m
Packages: 1282
Shell: zsh 5.8
Resolution: 2560x1440
DE: KDE 5.76.0 / Plasma 5.20.4
WM: KWin
GTK Theme: Breath [GTK2/3]
Icon Theme: breath2
Disk: 95G / 124G (81%)
CPU: Intel Core i5-8600K @ 6x 4.3GHz [51.0°C]
GPU: Radeon RX 570 Series (POLARIS10, DRM 3.38.0, 5.8.18-1-MANJARO, LLVM 11.0.0)
RAM: 2922MiB / 15892MiB

After restarting Steam it uses basically 0%
Yes, you got the exactly same issue like me.
Ah, it is definitely connected to the proton installation/updating/deinstallation
I switched all games globally to proton experimental and forced the valve certified games to use proton experimental and then uninstalled proton 3.16 and 5.13 and again the /home/$USERNAME/.local/share/Steam/ubuntu12_32/steam process consumes 100% cpu until I restart steam (and the shutdown of the process is delayed as well)
Hello @MartinX3, you've described the issue being tracked in #7372. Closing as a duplicate.
It might be worthwhile to follow https://github.com/ValveSoftware/steam-for-linux/issues/7372#issuecomment-696193644 and confirm that the thread name shows up as CLocalLibraryCr.
proton 3.16x1 2021-01proton experimentalx1 2021-01proton 5.13x2 2020-12
Your system information
Please describe your issue in as much detail as possible:
Since the proton 5.13 update and the introduction of the soldier steam runtime the steam process itself sometimes hangs with 100% cpu in the background.
I feel like mostly happens after waking the computer up after a night from standby.
Steps for reproducing this issue:
It's not really clear for me why this happens and when.