Maybe the PCB of the switch does not sit “well” in the retaining ring.
The PCB of the lighted switch is a bit larger than the PCB of the regular switch.
Please remove PCB and ring and check if the PCB can sink in into the ring all the way.
If the PCB cannot sink in all the way, it feels a bit wobly.
If so (or questionable) file a bit off from the sharp edges of the PCB => perfect round.
And to be sure, clean the outer end of the tube (body) that sticks into the tailcap-combo.
Is it a lighted switch?
Unfortunately they are incompatible with the biscotti UI, it’s only compatible with the 3/5 mode group.
There is a mod which needs an additional resistor.
Make sure everything sits flush and is tightened well, most of the problems are solved by tightening retaining rings.