Is the spring critical to lens placement. I clean the lens regularly, and the spring can make reinstalling the lens a pain. Am I doing any harm if I don’t install it?
most likely it is there to put some tension on the threads of the lens so it does not wiggle out. Other vendors have used O-rings to create friction for this same purpose. Your call.
I replaced the spring. There is too much play in the lens without it.
You could also try a ‘dot’ of nail polish to hold the lens from moving - we used to use it to “lock” potentiometers in place on PC boards…
not a good idea if there is not another way to set the Z axis/ focus the beam. If the OP has a Z axis adjustment then yes, anything to keep the lens from moving should work.