Hi there, sorry for delay, side tracked with actual sun shine here in the UK, then mowing the lawn and finally the new god of war game! :person_facepalming:

Tried both my sc600’s and both do have slop or movement in them off the O ring. Not more or less than pretty much other lights i have. Tried both the sc62 as well, also a PK light. Nothing felt untoward with the sc600’s or any worse/better. On the sc600 you can move the tail caps (wobble so to speak) and also pull/push for a little play in the threads before making the O ring.

Its a tough one, its a case of would need to compare directly to get an idea. As yours seems obvious and can presume worse than other lights with you noticing it. It does sound like you are on the end of some poor QC. ZL i am sure will sort, if not happy return for another. You wont be the 1st or the last! That is one of the reasons i try and get in the UK, in case any of the issues or LED tint etc etc crop up. I can return rather than sending China for example. Flip side is it limits me on choice and availability.

I have been pretty lucky out of the 7 or so ZL’s in total, only one i could not get on with was the sc5c mkII. The sc53w is not too far behind it either…………

Hope it gets sorted fast for you.