The blue locktite will only attack plastic if you get it on the plastic. Maybe you used too much?
Besides the gear that the screw goes into (for lack of a better term) is either brass or some
type of metal. And that's where I intended to put it until Sak came up with the idea of using
the star lockwasher to secure the screw into the assembly. I have used the blue locktite on
both the Tamiya class cars as well as the Mini Z's (1/28th? Scale) without any problems.
You just have to be very careful not to over do it!
Just a small drop of it works wonders.