The bug

Zombified piglins and wither skeleton avoid walking through fire or over magma blocks if there is an alternative (not much longer) path, even though these blocks aren't hazardous to them.

Note: In previous versions these mobs would never walk over these blocks, even if there was no alternative.

Exceptions

It appears under certain circumstances they do walk over these blocks, so make sure to avoid them when trying to reproduce the bug.

• In general mobs apparently walk through fire and over magma blocks if this is the only available path.
• Wither skeletons walk over magma blocks if there is only one, however when two are placed next to each other, they won't walk over them.
• If the alternative path is much longer (or they are already in fire or on magma blocks?) they walk through fire / over magma blocks.

How to reproduce

See also:

• Wither skeleton avoiding magma blocks (1.16.2).mp4
• Zombified piglin avoiding magma blocks (1.16.2).mp4

1. Build a "U"-shaped two block wide magma block pattern in the floor
2. Switch to survival mode
3. Give yourself fire resistance (optional)
4. Summon one of the affected mobs
5. Run over the magma blocks
   → The mob walk around the magma blocks to reach you

Code analysis

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