I’ve been having the same problem. Had a really close look at the cassette as turning peals. One of the teeth on the 13t cog was catching the chain and flicking it slightly. Quick dunt with a hammer and drift and it seems to be cured.
Be out tomorrow for a ride so will know then if its properly sorted.
One of my aunts donated her body for medical research. We had a service for her about 18 months after she died. Don’t know what happened to or if there were any remains.