Modifying the data of a frog using /data has a chance to prevent that frog from eating/noticing slimes or magma cubes until the world is reloaded. This does not always occur from seemingly random chance, however majority of the time it does.

Steps to Reproduce:

  Step 1: Spawn frogs using spawn eggs (preferably, spawn one each in its own designated area so each frog can be observed individually)

  Step 2: Modify the NBT data of a frog using /data.
Examples of commands that can be used to do this:
/execute as @e[type=minecraft:frog] run data merge entity @s {PortalCooldown:10}
/execute as @e[type=minecraft:frog] run data merge entity @s {variant:"minecraft:temperate"} ("minecraft:warm" and "minecraft:cold" also work)

  Step 3: Spawn small slimes using /summon slime ~ ~ ~ {Size:0}
(or /execute at @e[type=frog] run summon slime ~ ~ ~ {Size:0} if you have separated all the frogs)

  Step 4: Repeat step 2 and step 3 in the chance that all of the frogs still happen to function properly, frogs previously affected by the bug will still be affected by it.

Observed Results:

Not all the summoned frogs will eat/notice slimes or magma cubes

Expected Results:

All the summoned frogs should have eaten and pathfind towards slimes and magma cubes.

Additional Notes:

Reloading the world fixes the issue.