My Organisation under Calendar

Hi

It has come to light that under some users Calendar Share Permissions the My Organisation permissions have changed to Edit.   This has caused an issue with someone seeing something they shouldn't.

Most users are still set to Can View when I'm Busy but how did a handful of users have their settings changed?   They insist they didn't do it, they are not related in job role etc. there appears to be no correlation between them at all.   The accounts are a mix of old, medium and new so nothing has changed centrally.

I'm stumped, is there something I'm missing?   Is there something that would change this setting like Teams or sharing an invitation to an  external party?

Thanks