Counter out of range is typically caused by a bent card but it can also be caused by
i. A gate
ii. The card counters

Gate
Check that a gate (the steel thread) has not left its rest position (a small hole in the front panel) if you all of a sudden get an incorrect number of cards in a slot as shown to the right. This can happen after a card jam if you are not careful when you clear the card path.

It can also be that the gate is too high or low (depending on if the gate gets too few or too many cards).

Finally it can be that the gate does not move up and down as it should. You can use Diagnostics' gate stress test if you suspect that that could be the problem.

We suggest that you file a Report problem if you get an incorrect number of cards in a slot for no apparent reason.

Card sensors
You should suspect that the card sensors need to be cleaned if the card count on the screen does not reflect the situation in the board. A thin object sitting in a counter can cause the gates to behave strangely. c.f. the Maintenance instruction.