Hey so in the ticket, there wasn’t any mention of it being a non-neutral setup, so that’s definitely what’s causing the issues here as when no neutral is involved, full power isn’t being applied to the fan.
What you could try to do (again, not recommending you put a 2-1 on the fan as I mentioned in the message), is change parameter 25 to 1 (turns off the non-neutral throttle). However, I also don’t know how this will affect your fan.
My apologies for not probing further in the ticket and asking if this was a neutral or non-neutral setup.