I don't know anything about that throw, but I'll start the ball rolling with the smartass observation that whatever you keep having to tighten is what's getting loose...

If I had to guess I'd start with the strings are they tight enough? But that's probably not it.

...someone will be along to help you shortly...

Mitch

I appreciate the start. The strings are tight, but the actual nob to tighten or loosen the snares is what I have to keep adjusting (in the second photo).

That might be the original throw. I think that version of the lightning showed up near the end of the round badge era. I have some drums with the newer version of the lightning (the side throw version didn't last too long, maybe due to the problems you're having) but I have no experience with the earlier version so I'm afraid I can't offer much help. On mine the tension adjustment is all done on the butt side so my guess is either that side is slipping while the tension is off or else your snare cord is slipping and/or stretching in some way...not much help.

The catalog that first pops up in (1968 still RB era) shows straps holding the snares. Maybe that is a requirement.

Never liked that side throw lightning strainer. The center throw is at least a little better.

Sounds like something is coming loose. Check for stripped threads on both sides. The butt strainer should be all the way down when installing, then tighten to desired tension. Check during that process for slippage. Maybe that string is too thin?

Thanks for the feedback, guys. I was playing with snares on and off and noticed something today. When the snares are off, and I play the snare, the tension knob turns counterclockwise--on its own--as if I was loosening it. Obviously the stick-on-head vibration is causing this, but any ideas what could be causing the knob to turn on its own and loosen?

The sonic vibrations are doing it. Can you back the adjustment knob completely out of the strainer? If you're able to take some Teflon tape apply it the threads it will add some resistance to the knob, you'll need to experiment to see how thick you can go with it. http://www.sears.com/freeman-teflon-tape/p-00905026000P?sid=IDx01192011x000001&gclid=CLvH2ryiosoCFYwvgQodcccMMA

So pull the adjustment knob completely out and add teflon tape to it to secure it further, so there isn't any play? I took the strainer apart today to see if everything was okay internally, and it was. Where should I put the tape, and how much do I use? Obviously this is a defect/problem. Any idea why the vibration is causing this trouble? There has to be some faulty piece I could fix/replace.

I tightened the knob more to the shell, but that didn't help. Any thoughts? Besides taping the knob so it's immovable--and thus not functional--I'm not sure what else to do.

If done right the Teflon tape shouldn't make the knob immovable. The tape is very thin and will go down into the threads. Actually teflon is usually used to make things more slippery but a slight increase in the size of the threads should make them less likely to turn on their own.