Skywatcher 2" dielectric star diagonal question

[ecuador]

I have a Skywatcher 2" dielectric star diagonal that came with a scope and the side I am holding it the photo has a little play if I move it left right. It is very minor, but it does annoy me. Any idea if I can tighten it somehow? I don't want to force it, but in any case it does not look to me like that side screwes in. Anybody has disassembled theirs and knows how it's held together?

And to clean the mirror no such a diagonal, I assume you remove the side panels?

TIA

[Knighty2112]

Unscrew the collar and wrap a small amount of PTFE tape around the thread to stop any play. 

[ecuador]

I am not sure what you mean by collar, the tube I am holding does have what I could call a tiny collar on top, but I can't possibly get a grip on it to try and unscrew it. Unless I misunderstood.

[Knighty2112]

The tube end you have you hand on in the picture should fully unscrew from the diagonal. That part is what I referred to as the collar. 

[ecuador]

Huh, I gave it a hard CCW turn and it did start turning, but not like unscrewing, after half a turn it is now stiffer than when it started, no loose movement. Weird...

[Knighty2112]

OK. Not sure what's happenening with your diagonal, but all four different makes all unscrew with no problem, but don't have your make so not sure how it was put together.