I had fits with my EFW2 filter wheel recently. Among the problems: stopping between filters, not registering on #1, but randomly on other filter stops if centered at all, continued chugging along from filter to filter during a move. Was it software? Something wrong with the motor? No, it was a nick in my rubber band that surrounds the wheel. This was most certainly my fault for not retracting the gear fully when replacing the wheel after a filter cleaning. I turned the nick inward, now it seems to perform correctly through 10 trials of on-off-on. If you run into filter movement problems, check the rubber band.
But, just in case: Can we order new rubber for backup? Of so, how?