What could be wrong with my wipers

Sometimes, I can get the wipers to work just fine, then other times the right one won't go up. It will go just a little, like it is making an effort, but just can't do it. Could it have anything to do with the wiper arms being too long? I have the size that the auto store told me to buy but they are too long, the left one gets caught under the right one, and the right one hangs off a little. With winter coming I would really like to resolve this issue, if possible.