You need to use a med thread locker. It will stop the loosening nad will not cause anything to strip when you remove them. I use blue loctite and don't have screws coming loose. Don't use the red - it is semi permanent!

You need to start with clean, grease free screws and screw holes. I use a shot of motor spray (alcohol will work too) to clean the screws and holes before applying loctite. Use a cleaner that is evaporating so it doesn't interfere with the loctite curing. Loctite needs some time to set also - don't apply and expect it to cure instantly, it doesn't. Depending on temp, it needs a few to several hrs. I usually try to let mine cure overnite, that way I'm sure its set.

I use Tony's Screw kits - 1st thing I do to a new RC, replace everything with high strength alloy steel hex heads. Tony also sells individual screws.