The payload is an ASI1600 and EFW -- total weight under 5kg.
The coupling is screwed down tightly on both the EAF and the focus knob.
That is not the issue. When NOT under load, the spindle has about ¼” free play. That free play translates into about a 240 step backlash – that is excessive.
Please confirm that is not within an acceptable tolerance and OPT will replace it for me and ZWO will not have to do anything.