Remington Model 17 2with a sticky pump - should I buy? can it be fixed easily?

I am thinking of buying my brother-in-law's old Remington Model 17 20 gauge shotgun, but after trying it I found that in a horizontal position (regular shooting position) when I try to pump a shell it moves a bit and then won't go further. If I point the gun straight up or if I roll the gun so that the bottom/top is off vertical by about 30 degrees, it pumps just fine. My question is whether anyone might have any idea what might be wrong and whether it can be relatively easily fixed or whether I should pass on buying it???

Probably a problem with the shell lifter.

Find a schematic, tear it down and see what's going on.
Iirc, and it's been a very long time since I messed with one of those, the lifter can be installed wrong.

Parts are going to be almost impossible to find.
If it's really broken, it'll end up being an expensive fix if you have to have a part custom made or you'll have a gun to part out.

I agree with flathead 39 I have one of those old girls and is about the smoothest pump gun I've ever shot but I use it sparingly because of its age . A similar design to an Ithica 37 but I highly doubt interchangeable

Good cleaning and lube. See if anything bent when in it.