Hi Luis,
It is aggravating to me that Tina knew you are a beta program member and told you to ditch the beta program. That advice is completely against Microsoft's goals with the beta channel.
Please ignore that terrible advice. Tina ought to know better.
A major purpose of the beta channel is to discover problems and get them fixed before they get to the general release channel (current channel).
When you encounter strange, unexpected behavior, please report it directly to Microsoft PowerPoint team using the Feedback button found in the upper right corner of the window in Powerpoint, or from the Help menu. It is very important that you do this while the problem is exhibiting. Sending feedback this way sends metrics about the state of PowerPoint and your Mac as it is happening. This feedback is essential to Microsoft so they can fix bugs like this one. Test again with next week's build and send feedback about the issue every week until it is fixed.
PLEASE do NOT follow Tina's advice to dump the beta channel. Microsoft has spent a fortune building the channel. Having Tina trying to blow it up is a real problem.