On a multiplayer server, myself and two others were fishing for extended periods of time, and we gained a lot of experience from it. However, at one point Minecraft would stop letting us gain experience from fishing up items.

We have determined that we aren't getting any experience because our bar that shows the experience we get doesn't move. My friend was having the issue last night, jumped from a high place so her character would die, and then tried to fish and she had no experience after catching something. Her bar didn't even increase, it stayed empty.

I wish I was able to provide a video of it happening however this glitch happens randomly on our server. There will be periods where the fishing will glitch on one person and their experience bar will not move no matter the amount of times they fish. When this happens, we see the experience being absorbed by our character but the bar that shows our progress for the level isn't increasing.