I had trouble with my truck topper lock about every 2 yrs . ( dirt plus winter salt most likely)
1st time they replaced the guts of it 2nd time they got out the WD40 and a pick and had it working slick in no time .
A friend swears by white lithium spray grease been using it for years .
I always used graphite powder .
I think I'd try using WD and an air hose to try to flush it out ( easy on the air pressure).

 

WD 40........no problem.........but I have only been using it for 20+ years in every lock I have, house, cars, bikes, boats, padlocks.

 

I always use the provided squirt tube. Stick it as far into the lock as I can and give it a good flooding under pressure. You'd be suprised how much crap comes out of the lock sometimes.
You get little flakes of metal from the pins and various other chunks of crap. The Metal Protector dries out and won't get all over your key....makes a black mess of your pocket
I tried all the graphite stuff and it seemed to gum up after time making the lock sticky.
Each to his own I guess.
Russ