Both the left and right sides of the hotbar are often glitched out when I play on any of my worlds and servers. The left side is missing the left vertical border of the "one" slot execpt for a tiny little bit in the center, and the border of the right side of the "nine" slot is thinner than the rest of the lines. I am not sure if it is related or not, but it often seems to happen when I use one of my several addons. I tried to get a screenshot of it, but I could not because it seems to happen sporadically.