build log details of test are missing (TC 2019.2, .NET, NUnit 3)

We are running several Tests on NUnit Console 3 within TC 2019.2 and from one moment to another we are missing the console output of some tests without changing either the build configuration nor the test source code. so what can be the source of this issue?

Attached are two screenshots of the log showing the issue.

thanks for any help,

Kirsten

Logdetails okay:

no more details on same test: