Under most situations, this will not happen, but when it rarely does happen, we could just reboot the player afterwards instead of always requiring full unmounts.

Mmmm... I wonder if this can be done inside Hijack without confusing Emplode?

Confusing Emplode is exactly the problem: during a sync, Emplode is in charge of deciding whether to reboot, not the player; but we decided that having Emplode notice certain errors and reboot the player wasn't worth the risk (and it lays a heavy responsibility on the authors of third-party synchronisers: before the unmount behaviour was added in March 2001, several testers had their entire music partition wiped when fsck updated the root directory while the kernel held stale data).

Peter