Outlook Time zone appointment issue

Hi, don't know if this is the right place to ask this sorta thing, but here goes.. I have encountered an issue recently where if someone goes into amend the time zone of an outlook meeting, it seems to disappear from the calendar. However, I have tested this with one of my colleagues, and this doesn't happen for us. Any idea what this could be, we are using Outlook 2016 FYI, thanks.