I've been having this issue for a couple days now and I've attempted to fix it by resetting everything to uninstalling Photoshop, yet nothing seems to work. I've also tried finding an answer online but haven't come across anything useful, so this is my final place to turn to.
As seen in the pictures below, the gradient menu will not show completely to select other gradients. I've gone through each of the settings in the small part of the gear I can select, but nothing works. Any help will be appreciated.
Does your Pattern Select dialog work Okay? Sometimes they have similar symptoms. There's a post from Trevor Denis somewhere here that has helped several people, but I can't find the link right now. I'll keep looking.
This "pattern flyout bug" goes go back quite a ways...
Still with us I suppose: