After taking the a-lens down and examining the mtg bracket/knob system detail design here are my thoughts/opinions on the UH-380 droop issue:
(I've not done detail technical analysis, sharing my thoughts here)
1) Primary cause: I honestly don't feel there is enough bearing clamp surface on the lens boss/twist knob boss to the attach bracket.
The outside dia of each boss is approx 1/2 inch, you can see in the pict there is very little actual boss surface contact to the mtg bracket.
>>I recommend Panamorph consider re-tooling their lens case with more bearing surface by the threaded nut insert, and see if their knob vendor has "off the shelf" knob with bigger dia boss for the threaded stud to seat into.
This would make for more robust clamp design.
2) Secondary cause: Slight torque loss over time, possible due to vibration(s) of loud HT.
>>quick countermeasure is lock washer, more robust long term c/m might be 1.25 or 1.5 times larger dia knob itself so more inch-pounds of twist via hand can be applied.
Both 1 & 2 together, then some testing to confirm, should ensure no future droop issues.
As a design benchmark exercise I'm not sure what other similar lens have for their mtg system.
Both the case and the knob have approx 1/2" outer dia:
You can see with the slot there is very little actual bearing contact surface, ie, little grip surface for the coeff of friction to do its thing and resist the bending moment of the lens caused by the lens center of gravity being fwd of the pivot.
I tightened the knobs as tightly as I could by hand and I could still push the lens up/down with some effort on my part.
I think fully hand tightened you should not be able to rotate the lens up/down at all, that should be part of their system design spec.
I used quick c/m, lock washer, but fundamental issue of boss too small should be addressed by Panamorph in next design revision of their product
I wonder what sort of DFMEA's Panamorph Mech Engineers have done on this?
2 others that have read this thread have experienced this issue, it's worth while Panamorph to study for future kaizen.