Issues editing SharePoint calendar from outlook

One of our Directors syncs a SharePoint calendar to outlook. He has no issue creating a new item on the calendar, but when he goes to edit an Item he has just created he receives an error message.

"The Item cannot be saved because it was changed by another user or in another window. Do you want to save a copy in the default folder for the item?"

If he chooses yes, it saves the item to his calendar, then the SharePoint Calendar Item becomes editable if you try to edit it a second time. He then has to delete the saved item from his outlook calendar. Not a real big deal but He uses this calendar to schedule network engineers on call status pretty frequently so he would like a resolution. 

I have recreated the issue with my account also. Any suggestions? Screenshot included below.