Rear window interior trim too short

[ValiantK360]

My rear driver side window trim in the interior is not fitting right for some reason (I'm not sure if that's the name for it). It's the same trim as the other ones too. If I try to fit it on one side, the other side pulls off, it's kinda annoying. Did it shrink or something? Any ideas on how to fix this or where to buy a new trim piece like that in that color?

 

[pauly v.100]

Might be for an earlier Valiant, I think the rear doors were smaller. And its called windlace

 

[Sedanman]

Nah,that car is all original. I would loosen up the sill plate and pull the slack up then screw it back down