ZRACE cassette issues

[svanimpe]

Does anyone have any experience with this cassette?
https://www.aliexpress.com/item/1005001909541518.html

It claims compatibility with Ultegra, however, I'm unable to set it up (video: https://www.icloud.com/photos/#0Xgo95rrLWaAbvNoU114yBBMQ)

First, I noticed that this 11-34 cassette does not require a spacer (unlike Ultegra and 105 11-34 cassettes, which require a 1.85mm spacer on 11s hubs). I can reach all the cogs, so the limit screws are fine. However, I can make heads nor tails of the shifting problems. Sometimes it refuses to shift up, sometimes it overshifts and shifts up two cogs. Same happens on the way down.

[Nicoloc]

I have the 11-32 on my home-trainer.
So far no issues, but I remember that I had to thigh one of the three bolt that maintain the cogs together.
It was getting out of the 32 teeth dog and then the cassette wasn't spinning round.