Any ticking areas generated by entities using behavior packs are not removed by issueing the /tickingarea remove_all command.

To reproduce the issue: generate a world using the attached behavior pack. Explore the world for a bit. Run /tickingarea list. Run /tickingarea remove_all. Run /tickingarea list again.

The attached behavior pack is a behavior pack that affects all default and chest-minecarts. They should create a ticking area that never despawns. However, when the minecart dies (/kill @e), the ticking area also does not despawn, even though it was linked to the minecart. Now this might be intentional. However, the fact that you cannot even remove the ticking area using commands should, in my opinion, not be intentional.

I discovered this issue due to all abandoned mineshafts having their own ticking areas (due to the minecarts that spawn with them, creating unremovable ticking areas). One of my worlds now contains over 1500 of them, making the world rather unplayable due to TPS lag.