StackOverflow exception on startup with possibly corrupted extensions

What I did:
I upgraded our xwiki instance from 4.3 to 6.0.1. After our daily restart script ran, the service didn't come up again.
6.1 release just came out, so I upgraded to 6.1 which was successful. I re-configured ldap service and some other admin pages like search and then tried to restart the service again, which then failed again with a stack overflow.

How I "fixed" it:
I removed one of the extensions in the default permanent store called "org%2Exwiki%2Eplatform%253Axwiki-platform-user-profile-ui" - Xwiki just tells me it is initializing after every reboot, but at least it comes up now.

I attached my extension/repository directory here.