GPU freeze after 30m of playing Doom(2016) (379720)

Using Ubuntu 18.04, unstable padoka ppa, kernel 4.18.5-041805-generic, RX 56 I experience GPU hangs when playing Doom via Proton for about 30m when using gnome desktop, seems to last longer when using xfce desktop.
glxinfo:
Extended renderer info (GLX_MESA_query_renderer):
Vendor: X.Org (0x1002)
Device: Radeon RX Vega (VEGA10, DRM 3.26.0, 4.18.5-041805-generic, LLVM 8.0.
0) (0x687f)
Version: 18.3.0
Accelerated: yes
Video memory: 8176MB
Unified memory: no
Preferred profile: core (0x1)
Max core profile version: 4.5
Max compat profile version: 4.4
Max GLES1 profile version: 1.1
Max GLES[23] profile version: 3.2

Sound is still playing, can access system by ssh
dmesg shows:

[aug30 21:10] [drm:amdgpu_job_timedout [amdgpu]] ERROR ring gfx timeout, last signaled seq=8328960, last emitted seq=8328962
[ +0,000004] [drm] GPU recovery disabled.

Start by reproducing Doom (2016) through Proton on Ubuntu 18.04 with the reported RX Vega, kernel, Mesa, and desktop combinations. Compare the behavior under GNOME and XFCE, then inspect dmesg for the reported amdgpu ring gfx timeout. Done means identifying a reproducible cause and validating a resolution or clearly documented workaround.