Neo resistance off on the Etape today

I normally love Zwift but i just had to drop out of the Etape as my resistance was all off and I am incredibly frustrated. At a 2% gradient i literally could not turn the pedals, and on the 12% it would go from spinning at 150 rpm again to being unable to turn the pedals, every 2 seconds it would just keep flipping back and forth. this is the third time this has happened - and it starts mid ride. it is NOT the hardware, but something with Swift. could someone help me with this?