This happened today on one of my Windows 7 PC's (Microsoft Windows 7 Professional x64 Edition)1
This Workunit has also failed for 2 other so far:
6904306 (Microsoft Windows 7 Ultimate x64 Edition)
6928699 (Microsoft Windows 10 Professional x64 Edition)

Task 6926203
Application version: Machine Learning Dataset Generator v9.90 windows_x86_64
Run time 2 hours 17 min 39 sec
CPU time 2 hours 13 min 24 sec

Windows Error Log crash information:
Faulting application name: mlds.exe, version: 0.0.0.0, time stamp: 0x61233552
Faulting module name: ucrtbase.DLL, version: 10.0.14393.2990, time stamp: 0x5caeb96f
Exception code: 0x40000015
Fault offset: 0x000000000006e01f
Faulting process id: 0xaa8
Faulting application start time: 0x01d79aacac61dec7
Faulting application path: C:\BOINCData\slots\1\mlds.exe
Faulting module path: C:\Windows\system32\ucrtbase.DLL
Report Id: 1f1154f6-06b3-11ec-950f-bc305bbe8e5a

Stderr output

<core_client_version>7.16.11</core_client_version>
<![CDATA[
<message>
(unknown error) - exit code 195 (0xc3)</message>
<stderr_txt>
14:00:43 (4452): wrapper (7.7.26016): starting
14:00:44 (4452): wrapper: running mlds.exe (--nthreads 1 -c --maxepoch 128)
16:18:42 (4452): mlds.exe exited; CPU time 8004.645311
16:18:42 (4452): app exit status: 0x3
16:18:42 (4452): called boinc_finish(195)

</stderr_txt>
]]>

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Working on it. I find it interesting this one crashed after 2 hours of runtime. Thanks for posting these.