Chiming in to say I've just come on the forums to find some info about this - FFB trim is totally not working right now, either with the trimmer button or a hat. Basically it offsets the zero position of the stick, but then applies that offset to the current position. So as soon as you press the trimmer or use the hat, your stick position is doubled.
You can see this if you turn on the controls window, move the cyclic left, then apply left trim. The cyclic position moves with it.
I think for 'FFB trim mode', the current position of the stick needs to be read as an absolute value, not a relative value from the 'center'. Trimmer stores the '0' position that can then be used to calculate actual deflection. Or something like that!
Happy to try and produce a video or something/test anything that needs testing, if that's helpful.