How to revert before some activities were synced?

I changed phones recently and on re-pairing my device (a Wahoo Bolt) it decided to go through and re-sync all of several years worth of activities again to Xert.

This resulted in some that were properly detected as duplicates (and I assume ignored), but also some that got through and were not recognised as duplicates. I went ahead and manually deleted the ones that were actual duplicates, and waited while it said my fitness signature was being recalculated, but my signature remains skewed even after the recalculation.

Is there any way I can “rollback” this last sync of activities to get rid of the disaster they’ve caused to my progression tracking?

Edit: now that initial panic has subsided, I’m thinking this was likely because I still had my decay set to “none” as coming out of base, and thus the system re-calculated everything for the last ~2 years with that decay rate (?) I’m thinking that if I set the rate back to optimal, go back and remove one of the old workouts to force a re-calculation, then re-add it to force a re-calculation again that things should pretty much work themselves out (luckily I’ve had a few breakthroughs in the last week so should be relatively up-to-date) (?)