I had an issue that sounds similar to yours (on a Civic, coincidentally). The drivers belt would not catch in the latch unless I drove it in with a ridiculous amount of force. And even then, I'd make sure to tug on it, because sometimes it would pop out. I was afraid it would eventually stop holding altogether, so I had to do something. I ended up spraying a little PB-50 multi purpose lube in there, and working it by latching and unlatching the belt several times. Low and behold, the issue was resolved, and did not reoccur.

I did the above with everything still mounted in the car. A more elegant method would be to open up the cover, or better yet, do that and remove the latch so you can work on a bench. Then after cleaning, you can use some real oil (something extremely light, I would think). But the quick and dirty method worked for me.

Word of warning: There is a switch in the latch for seat belt interlock, and airbag. Probably not a good idea to get too much fluid of any kind on that, but the ones I've dealt with were all sealed. Maybe use WD-40 if in doubt. I just sprayed a bit with the red straw (not too much, mind you) and all was well.