Trainer not holding resistance

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Use trainer mostly on zwift
Losing resistance. Most notably on the flat. Elite direto. Seems ok on +gradients or maybe less of an issue.
On my preferred gearing I can spin at 95rpm and hold around 400 watts for 30 seconds. Recently after less than 10 seconds resistance drops off (on the flat) to under 300. I can either change gearing or up my cadence but it happens again.
Trainer difficulty helps a bit.
I use apple tv but have borrowed a lap top and it's the same.
I use my crank power meter and calibrate it weekly. My direto power meter is bolloxed. I can't get even pedal to the required speed of 33kph to calibrate it. Best I can't get is about 18kph. I've messaged elite to see if the power meter and gradient controller are linked.
I've also used the upgrado app to ensure I have the latest version.

Any advise welcomed.
Regards
Stuart

[[email protected]]

Ahh..tried a workout and erg mode not working