I have a Mantus Swivel attached to a Sarca Excel.
Occasionally I have similar reversals.
Firstly the swivel has an oval pin which has a higher load capacity to my G4 chain, so it won’t be the weakest link. It’s compact so I can’t see it would reduce the anchors workings.
Also after splitting the clamshell and cleaning/ regreasing the swivel this year, it has helped lessen the reversals. I think over time sand & mud
work into the inner workings.making it less effective.