Related issues : MC-208586 MC-208589
I made a small pool for some Axolotls and used some stair blocks in it. When the Axolotl swam up onto the solid block island I made and attempted to return to the water, MC-208589 came into play, and it "fell into" the stair blocks at the edge, getting stuck spinning at a vertical angle as seen in the pictures. It could not escape this situation and died as a result from lack of water.
The path finding and on-land animations, as stated in the reports posted and others, definitely seems to be the problem.
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Confirmed.
However player do crouch then there's down on the edge below.
Mob could try to do pathfinding (fixed for piglins and zombies in 1.16.4)
Axolotl do the same thing when they fall off the lava pool from below
Can confirm in 21w03a.
Can confirm in 21w05a.
Can confirm in 21w05b.
Can confirm in 21w06a.
Can confirm in 21w08b.
Can confirm.