My 2 cents as I faced such problem before (for a whole night), use 2x2 binning, start close to good focus with L filter, make sure your mechanics is suitable for your focuser (in my case max step was 1000, and each step is 100), set the exposure time for Ha, O3 and S2 filters to 15 seconds and most importantly in my case was enabling the coil power, as I discovered later that the optical train was heavy and always change position by gravity.

Since I made the above changes, my focuser works fine since then

hope this helps

Read More...