If it worked before, there is no reason why the plastic would be giving out or pinching it more unless you have the wires in the wrong place when you are pushing it into the grip (and therefore pinching or shorting the wires). It's more likely that the wiring or switch assembly is wearing out from metal fatigue.
I ended up replacing the switch assembly (came with wiring too) and it cost like $25. I also grinded away the plastic behind the trigger so that it could move back further.
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SHÖCK
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