Garmin Tacx Flux S - Resistance Drift

I stopped using ERG mode for intervals a while ago because I like to alter my cadence during intervals to shift the aerobic/anaerobic load. And I really didn’t like the death spiral ERG mode would induce. I have found having ERG mode off works much better, but I’ve noticed a new problem in that the trainer resistance tends to drift down as the interval goes on despite my keeping constant cadence and gearing. The change is less than a gear shift leaving me to fiddle with the resistance setting in the app which is tricky because 1) taking a hand off the bars alone changes my power, 2) there is lag between the app and trainer and 3) I don’t want to be fiddling with a touch screen with sweaty hands while I’m trying to survive a tough interval.

This really seems to me to be an issue with the Flux S so I guess my question is, have others had a similar issue with other models or brands? I have grown to despise all Garmin products but don’t want that bias to cloud my judgement.

Are you calibrating the trainer regularly, according to the manufacturer guidelines? I’m wondering if the resistance might be changing as the trainer warms up.