I found the issue, when porting to the new physics interface I missed passing in the gripped bone name to a function, which is why was only happening with PerBoneGripping enabled.
It wasn’t removing a delegate binding and was causing it to re-trigger every grip creating a loop.
Its fixed, just testing in 4.22 and then updating both branches, it will be live in a couple of minutes.
Think I should add a per bone gripping element in the example template to throw some tests at periodically.
Edit Patch is live on both repositories