Hello, ON Diablo 2 Ressurected i figured out the weapon swap bug. Every once in a wile me and others encounter an issue with not being able to use skills and swap weapons. The only fix at the time was to leave game and rejoin the game. Well i figured out what causes it and how to resolve the issue without leaving the game. To explain it i will detail describe what i did with my fury druid. OK so IF my mouse icon is on another characters name when i press my F key to turn into a werewolf it doesnt do anything, sometimes it tried to ask the person to trade. This event is what causes the bug. To un-do the bug you just put the mouse icon over any player and try to switch to werewolf again and the bug is undone. Hopefully this helps yall resolve the issue. 
Cheers.
EDIT: For other classes this bug happens with yall too with the same process, THe bottom line is, if you try to cast a skill wile your mouse icon is on a player in the game it will bug you out also, so just repeat that process to un do the bug.