Mine has also been doing this for the past few years and it's been getting worse. Mine is doing it because it must be off track just a tad and it catches at the very top of the door. Sometimes if I'm at highway speed and I roll my window up, it'll actually pop closed or not close all the way due to the vacuum. I'm going to have to tear into it and figure it out once it's warmer.
01 IS300 - MSM - 240k mile high club
Currently in: snow mode
BRZ Differential w/ 4.1 -- K&N FIPK Intake -- CXRacing Coilovers -- IS350 18" Wheels -- Greddy Lip [RIP :(]
Hotchkis Sways -- OBX Shorty Headers -- Custom Magnaflow Catback
"Gotta work on the nut behind the wheel before you start fixing bolts on the car"