There or sooooo many.
I remember a problem with the Roland G800 in that it wouldn't store Transpose in the performances. If you were in a transposed situation you couldn't change performances during the song without some quick button pushes. Much safer just to not use transpose.
On the PSR740, I had a lot of trouble at first wanting to change a style or sound on the fly and doing just the opposite because the wrong thing was on the screen.
On the PSR 8000, it was very easy to reach for a sound bank button and hit a registration change instead. Very interesting when it happens in the middle of a song.
In the early days of using arranger keyboards I almost always kept a duplicate in the car, just in case, but I can never remember one quitting completely. Occasional reboots, yes, but in close to 20 years of using them, I've never had one die on the job. Now if I can find some wood to knock on . . .
DonM