Look at posts 168, 169 and 170:
https://vborg.vbsupport.ru/showthrea...ff#post2576155
just the way it is, it's not really an "error" per se - I just live with it, but if you wish to eliminate the error, turn off all DBTech hacks before turning off your forum, and then turn them back on afterwards.
I turn my forum off only when upgrading anyway, and that is a rather fast process these days, so having this "error screen" as opposed to "the forums are now closed" is a definite inconvenience, but a manageable one.