When I use the sort button or even click on an item in my inventory, everything disappears. It all comes back when I open up a chest or other block's inventory.
I'm using Minecraft 1.8.9 with the mod version 1.60-beta-38, although I was having the same problem with the mod a few versions back (1.60-beta-30).
It was working fine for a while before the problem arose.

Added more information.

After more testing, I've decided that this mod is not the cause of the bug, but merely made it more apparent.

Please include the mod version, minecraft version, and any additional information that could be relevant.