Sea of Thieves (1172620) - Crash ~1 min after entering the sea, PartyXboxLive/rpcrt4 RPC_S_SERVER_UNAVAILABLE

Issue transferred from https://github.com/ValveSoftware/Proton/issues/9889.
@sandritodambolena44-dot posted on 2026-06-20T18:46:45:

Compatibility Report

• Name of the game with compatibility issues: Sea of Thieves
• Steam AppID of the game: 1172620

System Information

• GPU: AMD Radeon RX 570 Series (RADV POLARIS10), secondary GPU also present: AMD Radeon RX 550 (RADV POLARIS12)
• Video driver version: Mesa 26.1.2-arch3.1 (RADV)
• Kernel version: 7.0.12-1-cachyos
• Link to full system information report as Gist:

steam-1172620.log

https://gist.github.com/sandritodambolena44-dot/4213953a18bdcc656d99e8fbc3e5f2c2#file-gistfile1-txt

• Proton version: Tested on both Proton Experimental and Proton-GE, identical crash on both

I confirm:

• [x] that I haven't found an existing compatibility report for this game.
• [x] that I have checked whether there are updates for my system available.

Symptoms

Game crashes consistently ~1 minute after entering the sea, even when sailing solo with no party members (Safe Seas). The crash is an unhandled exception with a page fault on write access, originating in SotGame.exe (lock xaddl %eax, 8(%rdi) at offset +0x332b03). The backtrace consistently passes through PartyXboxLive.dll → rpcrt4.dll → sechost.dll, and the log shows RPC_S_SERVER_UNAVAILABLE exceptions alongside err:service:device_notify_proc failed to get event, error 1726.

Reproduction

1. Launch Sea of Thieves via Steam, with launch options PROTON_LOG=1 MESA_VK_DEVICE_SELECT=1002:67df %command%
2. Log in to Xbox Live account (succeeds)
3. Reach main menu and select "Set Sail" (solo, Safe Seas, no party)
4. Game enters the loading screen, loads into the sea
5. Approximately 1 minute later, the game crashes unexpectedly

Already tested and ruled out:

• Identical crash on Proton Experimental and Proton-GE
• Identical crash with a completely fresh/reset Wine prefix (no cached login/session data)
• Identical crash whether playing solo or with a party (rules out it being party-specific despite the DLL name)
• Forcing a single GPU via MESA_VK_DEVICE_SELECT and DXVK/VKD3D device filters did not change the outcome
• Verified game file integrity via Steam (no corrupted files found)

Full Proton log (PROTON_LOG=1) attached.

Originally posted by @kisak-valve in [#3931](https://github.com/ValveSoftware/Proton/issues/3931#issuecomment-4759656092)

Additional system detail: booting with amdgpu.dc=0 kernel parameter (required for this system to boot at all). This disables AMD's Display Core, which may affect how the kernel handles GPU/display notifications — possibly relevant given the device_notify_proc errors in the log.

Note: This appears to coincide with Sea of Thieves' Season 20 "Custom Seas" update (released June 18, 2026), which reworked the game's session/party system. The crash signature (PartyXboxLive.dll, session-related RPC calls) strongly suggests this is a regression caused by that update interacting badly with Wine's RPC implementation, not a pre-existing issue.