Power inconsistencies only using Tacx app with NEO 2T?

I found the feeling the Tacx gave me a bit inconsistent, but I attributed it to the fact that I honestly don't use it often, as only subjective perception, as I prefer to get outdoors, and only do so when the weather is really catastrophic outside or when my desire to go outside is very, very low. So yesterday I decided to do a workout, maintaining three typical intervals of approximately 250W. It started well, then became impossible. During the 250W cycle, it got harder and harder, until I ran out of gears and the strength to keep pedaling. Absolutely not logic resistance for 250W segment. I gave up, closed the app, and connected to another app. Everything was fine there; the same effort, the same effort, was logically maintained throughout the entire activity. Today I used it again with this other app and no problems.
Is there a problem with the Tacx app, or even when it's also run from a Garmin watch?

This last time I did it with the Garmin Tacx app running on macOS, but it had happened to me a while ago when I ran a workout directly from my FR955. I mistakenly attributed it to a firmware issue with the watch, since I always use the available beta versions. Now I see that's not the case.
I'm mainly surprised that I can't use it correctly from Garmin's own software, but I can from third-party software.

My trainer is a Tacx NEO 2T with the latest fw 2.6.0

Does this happen to anyone else? Thanks!