Processor: Intel(R) Core(TM) i7-9700K CPU @ 3.60GHz 3.60 GHz
64-bit operating system, x64-based processor
Shockbyte Minecraft 1.17 server: 4GB ram
There are issues with putting "/item replace entity" commands into repeat command blocks in version 1.17.
Ex: "/item replace entity @a hotbar.0 with minecraft:bow"
If a repeat command block is using this command to put an item in your first hotbar slot, you can throw the item and it seems to disappear from your inventory, and functionality of the item is limited:
You CAN'T shoot a bow
You CAN'T break blocks with a tool.
You CAN'T detect right-clicking an item with a command
You CAN attack players as if you have the item. (An invisible item with knockback 2 will still deal the appropriate knockback)
Depending on the situation, this issue can shift over to the 2nd slot. (For instance, if I'm replacing hotbar.0 with a bow and hotbar.1 with an arrow, I can seemingly throw away the arrow, but still shoot the bow.)
The only ways I've found to get these items back are to open your inventory and click on the slot the item is supposed to be in, OR open a chest. These issues did not happen when using "/replaceitem" commands in 1.16
PLEASE WATCH THIS VIDEO FOR FURTHER CONTEXT/EXPLANATION