Steam client triggers a new post install script for a Proton prefix already setup which never ends.

Your system information

• Steam client version (build number or date): Jun 7 2022 / 1654574690
• Distribution (e.g. Ubuntu): Debian Testing
• Opted into Steam client beta?: No
• Have you checked for system updates?: Yes

Please describe your issue in as much detail as possible:

The Steam client somehow seems triggers a reset of the install script for a game Proton prefix already setup, and ends up being stuck in a never ending loop (in my case at DirectX installation stage).

It does not occur every time, as can be seen in the standard output log attached ; here, the game "Biomutant" (Proton-rated platinum game AFAIK), I was able to launch it without the script being triggered the first time, but being triggered the second time.

The first time, I was able to play the game without any issue, the second time then, I am stuck on the Steam client looping at performing the "first time setup".

I have seen the same behaviour on another machine running Fedora with totally different specs, and the same issue on "Halo: The Master Chief Collection".

Steps for reproducing this issue:

1. Launch the Steam client through a terminal by typing steam
2. Click on play on a game (in my case Biomutant)
3. Observe another "first time setup" being performed and being stuch at DirectX installation.

N.B.: This is also the case when the reset init script is triggered by verifying the local files through the Steam GUI (Game Properties > Local Files > Verify integrity of game files).

FYI, here are my machine specs: https://gist.github.com/julben/a761911fd83c5448e13bafb62efa3e20

Here is the standard output of the client after successfully launching the game Biomutant, and exhibiting the issue the second time around: steam-never-ending-install-script-issue-stdout.txt
Here is the dump mentioned in the standard output: assert_20220721103149_55.dmp.txt

The Proton version used is the 7.0-3.

P.S.: I did not know if posting the issue here was best, even if Proton is involved. Please, move this issue where it belongs if necessary.

Edit : It seems that restarting the Steam client (after having to kill its process) sometimes works as a temporary workaround in my case (with Biomutant at least).

Reproduce the issue by launching Steam from a terminal and starting Biomutant or Halo: The Master Chief Collection with Proton 7.0-3, then review the attached stdout log and dump. Done means an already-configured Proton prefix does not repeatedly trigger the first-time setup or remain stuck at DirectX installation.