Elite Direto XR-T with Zwift Cog ERG issue

Hey all,
I’m seeking for some help with my trainer.

Bought a used Elite Direto XR-T this summer. Running a Zwift Cog (correct Elite version, ZC02-P-CCE000) with a 48T chainring up front, so 48/14 fixed. Using MyWhoosh on a MacBook Air over BLE. FTP set to 238.

The problem: in structured workouts I can't get past roughly 250W no matter what the target is. I set an interval at 381W, then 477W, then 605W. Resistance did not noticeably change between any of them. At a supposed 477W I was at 102 rpm with a heart rate of 130 — for reference, lab testing puts my aerobic threshold at 175W/140 bpm and my max ramp power at 310W. So the number on screen is fiction.

What I've already checked:

**•**	Pairing looks right — trainer shows in the power slot, the cadence slot, and the resistance/controllable slot, all connected  
**•**	Firmware is current  
**•**	Spindown calibration done after warmup  
**•**	Nothing else is grabbing the BLE channel  
**•**	48/14 at 100 rpm should be plenty of flywheel speed, so I don't think gearing is the issue

Questions:

1. Anyone running a Zwift Cog on a Direto XR-T? Since MyWhoosh has no virtual shifting, I'm locked in one gear — does that bite you in ERG specifically, or only in free ride?
2. Is a flat ceiling around 250W a known belt-slip symptom on these? No squealing that I've noticed.