Bringing this back from the dead because it turns out this does not happen when fishing with a harpoon. I believe the problem has to be a race condition of some sorts. This is just Fortnite speculation for what it is worth, but this is what I think is happening.
Fishing rod is cast, When it hits water the fishing rod bluebrint checks if its touching plain water or a fishing zone device. If the later a reference to the fishing zone is held
A loop and pause alongside a random number are used to poll weather to register a ‘bite’.
Player clicks to reel in fishing rod.
If the conditional statement evaluates to true then the fishing rod blueprint will either give normal loot if in plain water, If in a fishing zone then the blueprint triggers whatever function the fishing zone async is awaiting using the stored reference.
The fishing zone then goes through its bluebrint functions based on device settings, then fires the fish caught event. Meanwhile the fishing rod blueprint is waiting to receive the event so that it can spawn a fish/item on the hook and finish up by playing its reel in animation.
^-- This is where things get messy, hence why when the bug occurs the lure stays in the water and you are stuck in stasis (Fishing Rod places player in stasis for a few frames, then releases after event perhaps which never occurs leaving you stuck?)
The blueprint VM then needs to check if the zone has any subscribed events tied to the fish caught event. In theory it should have an event subscribed from the fishing rod, and one from my verse device.
The VM finds that fishing zone has my verse function subscribed to the event that is taking place and that it needs to call my helper class function. If the events are not handled concurrently it’s possible my function being handled first causes the fishing rod to never see the event fire and it breaks out of its current function never finishing the animation and locking the game (perhaps it doesn’t break out of the function and attempts to read a variable that is null at the time causing a runtime error)
TLDR; Fishing spots / rods can not be trusted and are effected by a bug that is hard to debug. I’ve submited a bug report for this, hopefully more people will run into this and we can get it fixed. I do have a private island pushed that can be used to test this: 7756-0815-9769