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The only non threaded connection I can think of is that I understand the camera connection plate to be a machined flat with a large knurled lock ring over the top, similar to the attachment of a Fastar secondary mirror in a Celestron SCT like my C9.25, if it was not done up nicely that could be a cause of tilt, or if anything at all got under one side. Parallel machining of parts would be critical for spacers etc.
I am not sure how touchy they are about focus, at F2 the critical focus zone will be tiny, but without the primary/secondary mirror combo of the SCT they may be in some ways easier to focus and probably don't shift as much with temperature changes. With the double magnifying mirrors, the SCT moves the focus zone by something like 120 microns for about a 10 micron movement of the mirror to focus. In the RASA, 10 microns should be 10 microns.
There is a specific light pollution filter for the RASA 8", they are sensitive enough about back focus that they come pre fitted with a flat glass window in place of a filter that you remove if you fit either the Celestron LPR filter (Goes in the same place as the glass window) or if you fit a filter drawer of some sort.
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