A bit more history:
It’s been working as expected then one of the CB servers in the cluster failed (it wasn’t really an issue as we have enough redundancy in the network and auto-failover) and suddenly the XDCR started going a bit crazy. We brought back up the failed node and since it’s been in that jigsaw behavior.
This happened once before and we solved it by completely removing the XDCR configuration and syncing from scratch with elasticsearch. Then it was fine until the same thing happened, a node failed (for as yet, unknown reasons) and back to this weird behavior.
It’s not critical since everything is still working fine, ES gets updated pretty quickly with new changes, but it’s causing far too much load until we create a new ES index and sync everything from scratch. Clearly something funky is going on. Hopefully some fresh eyes will have an idea.