When using automatic AFK fishing farms, the fishing rod sometimes casts even while still cast and spawns another bobber(so, two bobbers are floating now). It can also sometimes though rarely double cast. This can continue on indefinitely(I've observed it going up to 800 based on entity count) up until the game crashes.

The bobbers are not visual glitches. The bobbers also produce their splashing particles as normal bobbers do. They all (except the last spawned bobber, it returns as normal) remain attached to the fishing rod until the item held is switched with another.

I have not tested this yet on a singleplayer world. The Server is running with forge but has NO mods installed, essentially vanilla Minecraft only.

I did a /kill @e[type=minecraft:fishing_bobber] command and got atleast 1000 entities killed

What to do.

1. Make a server
2. Make an AFK Fishing Farm (I used https://www.youtube.com/watch?v=hTAHK2XnpQs)
3. Cast a fishing rod, holding down the right-click.
4. Wait until the fishing rod picks up a loot. It will eventually double cast.

I apologize for the file names, these were taken when I found my friend lagging out the server.