Just in case it happens to someone else and they know a solution. After an upgrade on the oacs-5-1 branch with changes from 8th of August til 21st of August, the groups table got emptied on my site.
Not sure if this happened by accident or by some script in the upgrade process, but I wanted to give people a headsup, if someone else stumbles upon this, to check it out before the next release.
Truth told, I did check it out for the last hour and could not find any connection in the code, so maybe it really was done by accident...
