Had my following list truncated by a client this past weekend. Discovered that the most likely reason was that I followed someone and the client (not Damus) sent out a kind 3 with a single “p” tag for the new follow. Looking into it I noticed that Damus and most other clients include a list of relays in the content for kind 3 events. But some don’t.

I planned to keep digging, but this sounds similar if not related.