Within the last year (2021) we had twice the case that the pressure spring which holds the stepper motor in the filter wheel was too strongly tense, whereby the connection motor/filter wheel placed the rotating filter wheel somewhat crookedly, so that the wheel had ground at housing. As soon as this tension was reduced by stretching the pressure spring, both filter wheels were running again. We hope that this factory defect, which is obviously very rare but does occur, could also be the case with you. We apologize for the error and your trouble.
Customer reply: We can report that the defect mentioned regarding the blocking of the filter wheel was obviously indeed due to the spring. We have opened the filter wheel as well as the drive part and stretched the pressure spring a little. Since then, the filter wheel can always be controlled without any problems, even at temperatures far below zero.