Some PPTX shapes are rendered incorrectly

[Ben9986]

Hi, I'm experiencing an issue when viewing a pptx document which contains some "math". The below image shows how it is displaying in the onlyoffice desktop editors.

This is how it displays using Microsoft Office Online:

As you can see the square brackets are being rendered as accented characters. Part of the reason is that the makers of the slides haven't actually used math symbols but rather three separate shapes as you can see after I've moved them below.

When copying the "left bracket" symbols and pasting into Github I actually get the three accented characters that were shown: ë ê é. I'm guessing this is a weird unicode thing.

Is this something that could be fixed or is this simply a weird quirk of how Microsoft creates/display shapes?

I'm using the Flatpak desktop editors on Fedora Silverblue 38.
I've attached the file in question below.

7.3 Rate of Diffusion - concentration gradients and temperature.pptx