xml project disabled for 3.6.1

Hello,
wie tried to open a 3.5.1 generated project with a 3.6.1. version.
Until now it was possible to use the project with both versions without any problem.
The project was committed to a SVN repository.

After upgrading a 3.5.1 version to 3.6.1 it was not possible to open the project neither with 3.5.1. nor with 3.6.1.
The roject file has been disabled in both versions.

Unfortunately no additional informations was presented in the log tab.

After a few retries (including uninstalling the tool and installing it again) we were able to open the project again with both versions.

Is that a known issue?
how can we avoid this situation in future when updating again a 3.5.1 to 3.6.1?

Thanks in advance.