Share Calendar not Update, log says DELIVER Storedrive

Hi Team,

I had a issue, At my Office theres a user ( User1 ). And then User 1 shared a calendar with other User ( User2 ). and then add several permission, so calendar is not only free busy

so User 1 can see User 2 calendar

first User 1 Send calendar Named "Example1"

after that User 1 update Example1 calendar subject and time into new subject " Example New" and then send to User 2

If I check at User 1 calendar view, the subject changing,but at the User2 Calendar ( from User1 outlook shared calendar )

User 2 still have "Example1" calendar Subject

I really sure message tracking log nothing wrong, I can see DELIVER STOREDRIVE at new calendar message from User 1 to User 2 ( Example New Subject ). 

Is there any issue with my Exchange (Exchange 2010 SP3) or the issue from outlook side?

please help team :)

Regards