I fear Sam’s probably right and Cubasis’ lack of Plugin Delay Compensation is very likely to be the culprit here. I also first discovered this issue with the FabFilter plugins (Pro-L2 Limiter) when I tried to apply it to my drum bus, and suddenly discovered all my percussion was out of sync with the rest of the track(!)
I recently purchased the ‘Unfiltered Audio’ suite of (desktop quality) plugins and tried them with Cubasis, but they are also mostly un-usable, because Cubasis is unable to compensate for the ‘signal delay’ these plugins introduce.
Strangely enough, I’m not aware of any other iOS DAWs that don’t have PDC built in - it very much seems to be a ‘standard feature’ of DAWs, but for some reason Steinberg have decided not to include this arguably essential functionality.
There’s a thread called ‘Cubasis PDC broken’, where there’s some further information on the issue. @LSlowak has confirmed that PDC is on the to-do list, but disappointingly, it’s been on the to-do list for the past 3 years, since Jan 2020…