Exchange calendar full view permission issue

[marka01]

Hello,

I have this weird issue where for some reason user1 is able to see a full calendar details of user2. There is no delegations under user2 on Exchange admin centre and he has not shared his calendar in any way from Outlook itself. I checked with PS the following:

get-mailboxfolderpermission -identity user2@domain.com -user user1@domain.com. Which confirmed with a message: "There is no existing permission entry found for user: user1"

Any idea what else I am missing to check? Could there be some group allowing this access and how do I find out which one?

I also checked there is no administration roles assigned to user1 or user2 on office365 admin portal.

[#2]

Admin roles don't grant you permissions to read other user's calendar, so check the standard mailbox permissions, folder permissions and delegation settings.

[#3]

Thanks Vasil,

I already checked with commands below and I do not see anything why user1 would have access to user2 calendar. Not sure what else to check.
Get-MailboxPermission -identity user2@domain.com:\Calendar
get-mailboxfolderpermission -identity user2@domain.com

If I try running directly