The anti cheat plugin is preventing some of the new 1.5 inventory mechanics from working. For example, now dragging and dropping a stack of items should distribute it evenly to all the spaces you mouse over. It appears to work, but then it puts it all back into one stack when you click again. The same goes for right clicking and dragging. I tested the mechanics in singleplayer and they worked fine, so It's not an issue with the update itself. If anything could be done about this, i would appreciate it since these changes make inventory management and crafting so much easier.