.xsessions-errors full of warnings

I have almost 400k lines of warnings (and occasional errors) in my current .xsession-errors file that look like this:

Fossilize WARN: Referenced Pipeline layout 363b15eea90822d5, but it does not exist.
This can be expected when replaying an archive from Steam.
If replaying just the application cache, make sure to replay together with the common cache, as application cache can depend on common cache.
Fossilize WARN: Referenced Pipeline layout 5824ee3337152992, but it does not exist.
This can be expected when replaying an archive from Steam.
If replaying just the application cache, make sure to replay together with the common cache, as application cache can depend on common cache.
Fossilize ERROR: Failed to parse pNext chain for sType: 1000320002
Fossilize WARN: Referenced Pipeline layout c34da37358ab927f, but it does not exist.
This can be expected when replaying an archive from Steam.
If replaying just the application cache, make sure to replay together with the common cache, as application cache can depend on common cache.
Fossilize WARN: Referenced Pipeline layout ff633201f6340b62, but it does not exist.
This can be expected when replaying an archive from Steam.
If replaying just the application cache, make sure to replay together with the common cache, as application cache can depend on common cache.
Fossilize WARN: Referenced Pipeline layout ab7c115aa56e8b27, but it does not exist.
This can be expected when replaying an archive from Steam.
If replaying just the application cache, make sure to replay together with the common cache, as application cache can depend on common cache.

Steam System Information: (too long to post here, sorry)
https://privatebin.at/?d00890c32a0829c6#9U9NG2GvESFUWuMza3Q3UPZTABCVm64zj5BRKvjqe5iX

No source files, tests, or entry points are identified in the report. Start by reproducing the Fossilize warnings and occasional parse error with the supplied Steam system information, then trace the warning output to determine whether the missing pipeline layouts and pNext parsing failure are expected or indicate a bug.