ST-402 Photometric Filter wheel problem

Hi,

I am getting back into using my ST-402. However, an old problem (present since I first purchased the camera) has  reappeared.

I thought I had it fixed, by tweaking thetightness of the washer on the centre wheel.

The (internal) filter wheel is out by 45deg (in a clockwise direction) on each filter, blocking the CCD chip from any light.

Might someone have a suggestion, before I go to the trouble and expense of returning the camera to SBIG.

John