ASTRO: Question on STL filter wheel

The filter wheel in my STL camera has suddenly decided to position the
lum filter at random. Never exactly the same spot but never too far
off. Result is a flat fielded image that makes the donuts look 3D in
the final picture. Each time I go back to the lum filter it is
positioned just slightly differently. Though a couple times it was more
than 2 degrees off. The other filter positions line up fine, just the
lum filter that is screwy. Since I'm using a SCT I suppose I could take
it out without much if any harm but I'd like to get this stabilized.

Any ideas?

Rick

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Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".