Dolphins get stuck when trying to jump from one pool to another

When one area of water is split from another area of water by a 2 to 3 high wall and the dolphin tries to pathfind / jump to the other one (assuming), he eventually stays underwater close to the wall till he suffocates.

Note: He isn't stuck on one block, he might swim left and right a bit, but always underwater and always close to the wall.

This specific setup here killed every single dolphin that we tried to spawn inside (5 in total). It takes up to ten minutes for the dolphin to start behaving weird, but it did happen to all of them eventually. The screenshots are from where the dolphin got stuck. We did not feed the dolphins, they were not searching for treasure. We did stand close to them in survival mode. There was no item close to them that they might pathfind to to play.

The screenshots are taken when the dolphins are currently suffocating themselves.

What I expected to happen was...:
dolphin should swim to water surface from time to time to get air

What actually happened was...:
stayed underwater and died

Steps to Reproduce:
1. try to rebuild whats in the screenshots, its a river biome and one section was just split off by a 2 to 3 height wall

2. spawn a dolphin inside

3. wait till it pathfinds itself into death (10min max)