Screen won't scroll

(I don't really think this is a bug I just don't know what board to put it under)

I occasionally have this problem when I play League on my Mac, when the game starts, I can't use my mouse to scroll. The camera will stay fixed in one place unless I hit space to center in on my champ, or intervene in some other way

I know the camera didn't get locked by mistake because I am still able to turn that on and off (with Y or by clicking). All my keys (QWER) work normally and I can right click to attack, however, whenever I need to left click on anything (minimap, shop, etc) I have to double click. I can still scroll in the shop so I don't think it's a scrolling problem with my mouse.

I have no idea what causes this problem because it seems to happen randomly, and there will be long periods of time when it won't happen at all. There seems to be no correlation between the champions, maps, modes, etc that I pick. This really messes me up and if you have any ideas about how to fix it please let me know.