3DPrinting

I was monitoring this print remotely (Bambu P1S), so I'm not sure what actually happened. It's possible that it failed for other reasons, and then the tool head got tangled in spaghetti and disassembled itself.

It's held in with two fairly strong magnets, I don't think it falls off on its own. If a print falls over and catches on the extruder it could push the front off. I've had it happen for that reason.

Personally..... I'd just have left it off if I was them. I can't imagine a little plastic shield helps hot end temps

I've printed on mine for nearly 1000hrs now, never had an issue with that or prints not sticking. Just have to prep it well and make sure there are no scraps under it.

Normally the toolhead should never hit any object. If it does, and the cover detaches, it can be detected and the printer stopped before any significant damage is caused. Fallen off cover > broken machine.

The cover needs to be detachable to change or replace the hotend, and you need to have the cover for basic protection and better airflow control (I assume), and it's best practice to have a sensor to protect from user error. If the sensor is already there, why not also use it during the print?