nunit-console: Getting exit code -5 with NUnit console runner 3.8, using NUnit 3.10

The console runner exits with exit code -5. However, when I lookup the source here, this is commented out. There is no additional information with the exit (no errors, apart from the usual from failing tests).

My project uses 3.10 most recent NUnit framework, the console runner is 3.8, it is run from within TeamCity. What does this exit code mean and if it is valid, is it possible to give some more information when this situation occurs?