Some resistance issue going on here - HELP!

I’m running a Kickr 18 and I’m trying to find a nice gear to hold a comfortable cadence that as soon as my cadence hits around 85-90, the flywheel speed and that of my stroke seem off and I have a sense of ‘chasing’ or ‘slipping’ between the turns of the crank. It’s hard to explain but it’s like I have to go to a harder gear (up or down, not sure what the correct lingo is) to ensure a constant feed of power to the flywheel which I don’t experience when riding on a road or trail. It’s like it loses sudden resistance and you’re just spinning “air” if you will.
It’s a pain because I’m constantly going up and down gears to find that sweet spot and I just want to stay 1. I’ve tried turning off the gradient functions but it wasn’t as successful as I would have hoped.

What’s your trainer?

Good question. I’ll add to the main post. It’s a Kickr 18

In that case it sounds like something is wrong with the trainer and I’d suggest contacting wahoo who should be able to determine if there is a problem. They will likely get you to do a structured ride and ask you to send them the fit file.

What’s it behave like in erg mode?

I’d also try it on any other training/simulation platform (free ones or free trials etc) to make sure it isn’t isolated to zwift.