I've noticed this as well, but it is usually caused because there are no applicable actions to that item.

I'm having this issue as well. I now have a screw driver in my hand and a can of spaghetti in my inventory and I can't open the can. Can screw drivers be used to open cans, I thought so.

I think this is more of a player feedback issue. Having some kind of "You can't do anything with this." message would be nice.

I also have this issue. I cannot interact with anything in my inventory weather it's dragging and dropping or drinking from a canteen, I can do nothing in my inventory. This means to reload a Mosin I have to drop the mag on the floor and look at it and then select "load in" or whatever it is. YOU ARE NOT ALONE FRIEND!

I think I found the problem. If you open your inventory, do not hold tab. If you release tab, then it should work fine. I have also experienced this prob, but if I dont hold tab, then it works fine.