Thanks all - for fyi in my two photos the second one is when the break is engaged, knob covers the threads, looks normal. The first photo is what happens when I try to loosen it by the knob...the knob just unthreads itself till it comes off. Then I get my pliers and manually turn the shaft to loosen.
In the photo you can see a break in the thread, inside there is something that could look like a screw, a small cylinder of metal but no screw head...should have taken a picture could be a set screw. If it was a set screw how would one screw the knob on, past the set screw, but then ensuring the knob doesn't back off when loosening the break? I'm not sure how a set screw would work in this instance.
@jviss is loctite a permanent solution (permanent in a way that I'll regret later)? Or removable at some point?
I guess if it was "permanent" it wouldn't be a problem because if I ever need to replace the whole pedestal break system I'd be doing that from the top, under the compass.
I'm also wondering if I were to buy a brand new edson break, what keeps the knob in place while loosening?