Is your gimbal lock parallel The gimbal top section ?

[Dadcat]

This is mine

You can see it's not flush and yes its plastic is slotted into the metal gap

I can make mine look like that too if I try, but if I squeeze the clamp and gimbal base together it straightens out.

If you can't do that maybe there's some mold flashing on one of the parts keeping the clamp from seating correctly.