I am using AdGuard filters only, however DNS was enabled. Disabling it didnt help. Then I started messing with some settings (excuse me, im pretty new to Adguard, never read a tutorial etc.).
Turns out, that I had the option "Filter blocklist only" in HTTPS filtering network settings enabled for whatever reason. After disabling, the adblock warning, atleast in userupload ,didnt pop up again. So it works smoothly now. Have to test on other occasions. However, when HTTPS filtering is disabled completely, the adblock gets detected again.
I have to research a bit into Adblocking afterwards. Dont even know whats HTTPS filtering about. But anyway,Thanks for helping me @Blaz