Hi Jim
The trainer adjusts resistance by moving a magnet past the flywheel, and does that using a worm drive mechanism with a stepper motor. It’s prone to sticking (mine stuck within three weeks of ownership) and that can produce all sorts of strange effects. The trainer calculates power based on where it thinks the magnet is not where it actually is, and that leads to some strange effects (nothing to do with Zwift).
There is a whole thread here with some helpful info…
I fixed mine by taking the cover off, wiggling the worm drive with some long nosed pliers which freed the mechanism, then spraying it with dry PTFE lubricant (and keeping fingers crossed). Elite support are actually pretty good if you email them as well.