Dylan Fijal

For worlds created before 20w17a and are opened in 20w17a, the heightmap can be fixed by selecting the affected world, clicking 'Edit', then clicking 'Optimize World'. Ensure that the 'Erase Cached Data' box is ticked, then run the optimiziation (I'd recommend clicking "backup and load" over "I know what I'm doing", but that's up to you). In my experience, this solved the issue on multiple affected worlds.

Can confirm, I'm having this issue in Minecraft snapshot 20w18a. When I attempt to reel in when getting a bite, the player character's arm swings, as though to reel in, but nothing happens. The bobber can only be reeled in once the bite has been lost. I attempted fishing with both an enchanted fishing rod and an unenchanted fishing rod, but I had the same issue with both.