The Bug
When a Carrot on a Stick or Warped Fungus on a Stick breaks, it no longer gives a Fishing Rod back. Instead, the item completely breaks. This could be due to the fix of MC-272430.
How to Reproduce
Obtain an almost broken Carrot on a Stick:
/give @s minecraft:carrot_on_a_stick[damage=24]Or an almost broken Warped Fungus on a Stick:
/give @s minecraft:warped_fungus_on_a_stick[damage=99]Saddle a Pig or Strider, depending on the item you have, and ride it in Survival mode. Right click the item to boost the Pig/Strider.
❌ Note how the item is destroyed with no Fishing Rod in its place.
Can confirm.