Oh, and this. The problem is likely NOT the soft metal, but most likely rough threads on the screws chewing up the metal.

The solution to this is to get a threading die and chase the threads using a die. You can buy a die kit from harbor freigt.

Just oil the bold or screw and screw the die down the length of the screw or bolt a couple of times to uniform the threads and knock off any burrs.

ANY screw or bolt that has rough threads will damage just about any thread you put it in if the material is softer.

I bought an inexpensive set of taps and dies many many years ago and ANY time I encounter a bolt or screw that will be removed or turned frequently, I always chase the threads smooth. THIS is the key to not only eliminiating the problem you have, but getting these kinds of connections to work SMOOOTHLY! Having a screw or knob with dress threads greatly improves the smoothness when you DO have to turn or make an adjustment.

Good luck.