I need to downgrade my Forerunner 255's firmware

My Forerunner 255 updated on its own despite the ''auto update'' function being off!

I've had it for about two years and it had never updated before. The other day, I put it to charge and when I took it back, it turned off on its own, then turned back on with a gear icon on the screen, and proceeded to update itself.

One week later, the exact same happened to my wife FR 255, who also had that function off.

I am very pissed as it is very bad now!

- The battery lasts about half of what it used to.

- there's that new function called Naps, but it tracks naps very badly and says I'm sleeping when I'm just sitting watching TV, video games, etc.

- sleep tracking is way worse than before : I manually put it in sleep mode at 9.30pm yesterday and this morning it says I went to bed at midnight... Doesn't track when I wake up either, unlike it used to do before.

- some insight are bonkers. Yesterday, after doing a 34-km walk, it told me ''you still have plenty of body battery left for the rest of your day'', even though my body battery was 16.

- the ''controls'' screen looks bad, now when you have mode icons that the circular screen can show at once, it removes TWO spots, one that is replaced by 2 slash bars '' // '' and one that is just a gap between the first one and the last one of the circle. It used to be so much more harmonious, with just a bar and a ''+x'', x being the number of icons that are not shown.

The only thing I like about that firmware version is the new way to input reps and weights while doing a strength activity.

Given how messed up it is, we need to revert back to the firmware it had before, which was 16.xx

Please, tell me there's a way to do it.

Thanks heaps!