[rewritten/resolved]
ok. . . i've identified the issue causing slowdowns to max 6hrs interval, its actually single damaged Salvager. [check for NPR's damaged ships]
I wanted to make simple procedure to delete problematic ships from DB with all related records, but after deleting all data referencing to shipid/fleetid, game was still generating several null references from functions i couldnt identify...
Which left me to just change NPR in question to Human player, deleting that fleet, saving game and returning NPR to NPR. No errors detected, hopefully NPR will work on..
Leaving this for a chance it will help somobody or if somebody wants to share all fleet/ship relevant tables to delete..