On 1.20.1
If you enable putting items in the offhand slot in the config file:
When you hold a placeable item in your offhand slot and then toggle shield, if you continue holding your sword and try placing the item from your offhand, the amount of item in offhand won't actually change. Sometimes it doesn't happen though. Sometimes it even removes everything from the offhand slot.

the plugin doesnt save blocking state across restarts meaning if you hold right click to swordblock and open pause menu to disconnect and server restarts before you reconnect you can casually take out the shield from your offhand

1. Please fill in the issue template properly. We need to know the details of your setup to be able to help.
2. @s0me0ne-coder that sound like a completely different issue. You can open up a new ticket for that.