Mob surveillance stops after the world is rebooted.

If the player starts watching the mob in the Spectator mode and skips the world, then after the replay, the mob will stop being monitored. For reproduce:

Switch to the Spectator mode with the command : /gamemode spectaror or use F3+F4.

Summon any mob (let it be a Parched) with the team /summon minecraft:parched.

Move into it, i.e. start observing it.

Continuing to look from his face, restart the world.

After restarting the world, you will stop watching the Parched. Most likely, this is due to the fact that when a player exits the game while he is watching someone, he is instantly evicted from the mob on behalf of whom he was watching, well, in principle, this is logical, like a player in the Spectator mode looks from the face of the mob, then exits the game and therefore he is instantly evicted from a mob, because how can a player watch a mob if it's not in the game? So maybe that's how it should be.