Why are some powerpoint slides not showing correctly in presenter mode when MacBook is connected to a projector?

Greetings!

This is the first time I have ever tried to post a question to this forum.

I have a Macbook Pro (bought in late 2013) running OS 10 High Sierra and Microsoft Office for Mac 2011.

When playing a power point presentation in "presenter mode" with the MacBook connected to a projector, some slides do not display properly on neither MacBook screen nor projector screen.

-This occurs randomly.

-Some slides might miss a picture

-Some slides will have the text lines superimposed on each other or just missing altogether.

-This has now happened on two different occasions with two different projectors.

-Prior to both presentations, I toggled through all slides and they looked just fine on both screens.

This NEVER happens when playing the presentation on the mac itself without being connected to a projector.

Has anyone encountered a similar problem?

I am running the Mac and the projector both connected to AC power

Microsoft Office 2011 is updated (although not supported any longer as of fall 2017)