Wattbike Atom and Zwift resistance

Just bought the Wattbike Atom and paid my first full month subscription to Zwift to sort myself out with consistent riding this winter.

Read a lot of threads on here but not seen any definitive answers on random resistance changes. I can be cycling on the flats with absolutely no gradient and the bike randomly increases resistance, I pedal harder for a second and then it changes back to normal as if noticing the increased wattage. I also notice random small jumps in RPM that drop back down again instantly.

Has anyone actually got a response on why this happens or what the solution is? I should absolutely just be able to hold my power and speed (as I would do on the road) and get into a rhythm.

Any views guys?