This happens to a lot of people.
Therefor i've Always did the following solution, before turning the screw in you'll have to turn the screw anti-clockwise.
When you do this you will feel the screw popping in the thread that's been there before unscrewing the screw out of the chassis or other parts.
When you feel the screw has popped into the thread then you can thighten the screw.
The next step is also very importand to do.
When you thighten the screw you'll need to focus on the feeling when you are thightning the screw into the chassis or other parts.
When you are experiencing that you'll need to add extra force for fully thighten the screw is the moment you'll need to stop thightning the screw.
it's possible that you still can thighten the screw for another fourth of a full turn but that's in most cases more then enough to stop thightning.
When you keep this in mind you will be able to use the same parts or chassis for a very long time.
I have never stripped one hole of my TT-02 chassis, just by doing that what i've discribed above.