I encountered the opposite the other day. Accidentally paired my vortex smart as cadence instead of my Garmin sensor and the cadence reported maxed out at 35.
“We stopped displaying estimated cadence (which is what most smart trainers use) as it very rarely reflects reality. Zwift, in game, only shows cadence for dedicated cadence sensors or those on power meters”
I have moved back to my BLE Wahoo SC device for cadence