The bug

If an entity identifies a path, they will always attempt to execute it, even if it later becomes mostly (not fully) impossible, unless the player interacts with them via lead (moving them dozens of blocks), breeding, or leaving the world.

This report is not MCPE-46805 or MCPE-45527, but does add to the problem.

There are many ways to reproduce this, including some that may not be listed here:

Method 1

1. Make a large cubic area enclosed with any block or fence (suggested 11 x 11)
2. Spawn about 32 of any equal sized mob
3. Wait 1-3 minutes

At the end, every mob should be pushed towards one side or corner of the cube, constantly colliding off of each other, until the player interacts with them (in the ways listed above).

Method 2

1. Make an enclosed 3 x 4 area
2. Set up a tripwire on one of the two shortest sides
3. Link it to a command block that teleports any mob (that will be used later) back into the box
4. Place fences above the tripwire hooks, but leave the block above the tripwire (the string) clear
5. Spawn a mob that's taller than one block
6. Wait until they pathfind outside of the area

At the end, that mob should never stop attempting to leave the box until the player interacts with them (in the ways listed above).

Method 3

1. Spawn a mob that can be leashed
2. Leash the mob
3. (optional) Place the lead on a fence
4. Wait until they pathfind

At the end, that mob should never stop pathfinding in the same direction that they're attempting to, until the player interacts with them (in the ways listed above).

Method 4 (relates to method 3)

1. Spawn a mob that can be leashed
2. Leash the mob (do not place the lead on a fence)
3. Place a fence and any full block next to each other
4. Stand next to the fence as close as possible on any side (except for on top of the full block)
5. Wait for the mob to pathfind

When the mob goes too far on the lead, they will come back and jump onto the fence (the block that the player is in) endlessly, until the player interacts with them (in the ways listed above).

Method 5

1. Spawn a mob in a body of water (a generated ocean coastline or river is recommended)
2. Wait until they pathfind onto land
3. Quickly place a full block on land, directly in their way from leaving the water

At the end, they will endlessly jump in the water until the player interacts with them (in the ways listed above).