PDF focuser weirdness

Suddenly my (fairly new) FLI PDF focuser acted up:

1.  I move the focuser to 2500
2. Then I move it to 2501 (using the FLIFocuser app to make sure that this isn't a problem with some other software) - I can see that it moves first to 2506 and then back to 2501 (I guess it has a 5 step built-in backlash compensation?)
3. Then I move it to 2502But now it only moves it to 2496 !!!!
   It somehow didn't execute the +1 step from me or +5 step from the first part of the backlash compensation. But only the -5 backlash compensation.

And it happens A LOT! I tried all three speeds (Slow, Medium, Fast) or I tried other step sizes - always the same.

Asked Richard, Richard, Jim and John and also sent an email to FLI...