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The reasons were discussed in Q8 thread.
Most cheap can-shape flashlights a machined without threads synchronization. I.e. switch place is milled with separate machine or separate setup and have random position relative to the threads start point.
Battery tube is made with same way.
As result you have random angle between switch and tube flatness.
In Q8 design this problem is even bigger than ever, because tube end forces down the driver pcb so tube angular position depends from driver thickness.
Using combine machines with minimum setups can fix this problem, but sometimes design is not suitable for this.
If flashlight have a removable tail cap (as Q8 have), a spare lanyard ring that can freely rotate looks like cheap and easy solution.