Removal of messages is broken in RouterOS 7.8:
[admin@MikroTik] > /tool/sms/inbox/remove [ find ]
failure: Interface not running!
Of course the interface is running. Toggling the auto-erase setting
fixes this until next boot. So let's add a workaround...
Reported to support (SUP-110828), but not (yet) acknowledged. 🤨