Lord Nerek

Yes this has happened to me too, I noticed that this mostly happens when the reeds were in water. Has that been the same experience for you?

I went to pan 10 blocks of bony soil and on my first pann I got a flint arow head and then nothing for the rest of the panning. I started a new world and went and grabbed 4 blocks of bony soil and panned them. I got a bone on my first attempt at panning and then nothing after that. Gravel seems to work fine.

Edit: Sorry this is on 1.17 experimental 

Sorry, was hoping that would help you, I am able to play 1.17 now smooth. I do have a bit of a beefy computer.

Interesting development  Avg FPS 11, but if I turn my shadows option up from low to medium/high/very high my fps jumps to 144fps. If I turn my shadows back down to low I drop back down to 10 FPS. 

High Shadows 144fps

https://imgur.com/j1WZeVZ

Low Shadows 9fps

https://imgur.com/vvEO5FE

I have the same issue. It speeds up if you lower your resolution, but the game looks terrible. At 100% resolution I get 7 fps, at 25% I get 24 fps, and at 6% resolution I get 84 fps. Game looks so burry its practically unplayable for me at 6%. 

Also the reflections on water flicker in and out as the body of water gets to the edge of the screen.