It's hard to describe this bug, because it doesn't always happen either.
In custom projects, I finds that Retest phases always fails to pass, so much so that it deletes all the strategies, and since my strategies are generated by template, I can estimate that it is unlikely that they all fail. So I copy the strategies from the custom project into a separate Retester, using the same Retester settings config as it is in the custom project, Some strategies do pass the test.
Very strange.
this could happen if you have a smaller number of max optimization steps. I think this is the only possible case, I cannot find out what is wrong unless you attach some strategy that failed in cstom project (turn off deleting of the failed) and passed in normal retest.