Hmm: that's unfortunate, Lena. Let me try another angle.
Do you happen to create your Projects from Templates? If so, you might consider our Sync Template AtApp, which (among other features ) would allow you to sync the Predecessors on the Template Tasks out to the Project(s) that need to be repaired.
That's not why we built it, mind you. Knowing when your Templates are ready to roll out (especially your first few) is normally a rather daunting decistion to make: no one wants to jump too soon, and then have to correct a shwack of Projects manually afterwards! So, the intention of Sync Template is to give people the freedom to Just Get Going with Templates, knowing that they can then improve the them as they Get Smarter and sync out to in-flight Projects.
However, if in this case, you can use it to recover from a bug that might be around for a while, I'd be equally pleased.
Regards,
Doug