An error occurred while saving the commentJeff W commented
I already posted this in another thread, but wanted to share my findings here as well.
I have similar issues with end users in my office. The OWA work around allows them a temporary fix, but I found updating my Office desktop application is what breaks it.
I thought it was due to a teams update, but after updating teams I was still able to change a single occurrence within a series.
I updated my Office from 'Version 2007 build 13029.20308 to 13029.20344' and started having the exact same issues my end users were reporting.
It seems as though there was an issue with the latest office update that breaks the teams plug-in ability to change a single occurrence of a meeting series to a teams meeting.