I notice about something similar this week, APs going up and down by a little bit.
I am unable to track which one was that, but I believe it is one of the repeatables in EoD triggering the issue?
Currently I am sitting slightly above 44k, had most EoD AP finished (missing repeatable Kappa/Unchained from Kaineng, Shrine Guardians and backpack from Echovald, and Avid Saltwater).
Since on my account I had most of the APs in EoD are finished, and my daily routine lately only contains meta events, none of the remaining APs are being worked on.
As far as I can tell, the ones that I finished lately are repeatables (Seitung meta, JadeMech/Purist/Meta in Kaineng, and the lighting ones), dailies, weeklies (Jade Statuettes), and SAB dailies, but none of these should no longer provide APs for my account.
Hopefully this information can help to narrow down the issue.