I bought a used QU16 that was in great condition and worked perfect but a day or two I head a screw falling around inside.
I did a full disassembly and re-seated connectors ect. while I was in there.
I found the screw and in my case it was a screw that hold the side rubber end caps to the
framework.
Yes it’s a lot of screws and they come apart kind of like a puzzle!
Just to open it up and try to shake out the nut take all the stainless steel allen cap head screws around one side and pull the end cap off. You may need to crack some of the other screws loose a little to get it out.
The screw that’s missing on yours is the screw that held the plastic clip that can be used to hold the power cord in place.
The threaded insert looks like it popped loose and fell inside.
Yes that could be very bad in the wrong spot!!
Who knows how long the screw had been loose in the QU16 I bought.