Been fiddling with zds for a few days now, and a few of the things I've tried it with have been spitting out interesting errors. In short, zds is setting the since field in #commit events to the repo's previous cid as opposed to the rkey. This can be seen through PDSls' firehose viewer: https://pdsls.dev/firehose?instance=wss%3A%2F%2Fzds-pds.atserver.farm&cursor=0
Doesn't seem to be causing errors in as many places as I'd've expected, but does on anything doing a strict deserialisation on that field.
Source: https://atproto.com/specs/sync#commit-events and https://www.ietf.org/archive/id/draft-holmgren-at-synchronization-00.html#section-4.4.2-3.5.1
nice catch!
#commit.sinceshould have been the previous reporev/TID, not the previous commit CID. it should now emit the correct value for new commits