CKAN introduced a system where you can symlink stock files across instances. Therefore KSPBurst should not store per-instance output in there.
I hit this when running more than one such instance at a time:
[LOG 10:17:57.333] [KSPBurst]: Burst stdout:
[EXC 10:17:57.336] UnauthorizedAccessException: Access to the path "C:/Program Files (x86)/Steam/steamapps/common/KSP Stripped/KSP_x64_Data\Plugins\lib_burst_generated.dll.bak" is denied.
CKAN introduced a system where you can symlink stock files across instances. Therefore KSPBurst should not store per-instance output in there.
I hit this when running more than one such instance at a time: