Federation seems to have broken down

I'm experiencing some odd behavior. Lemmy communities on my server seem to have stalled (no new posts and or comments) since 2 days.

I went ahead and upgraded lemmy to 0.19.5 and postgres to the current version but to no avail so far.

.ml got banned by fail2ban but I set it on the ignore list now. any ideas where to start looking for the problems? I checked for the other big communities and they're okay it seems.

I can of course start adding logs in here but I would love to know which service or log I should start with.

Thanks for reading. Have a good one.

Edit: outgoing federation works. this post made it to ml in seconds.