Hi Benjamin,
ActivePresenter uses MathML to create Equations.
This is a hack, but you can open the .approj file in a text editor and change the MathML manually. Be VERY CAREFUL not to change anything else.
Example:

Make sure that you don’t have the file open in ActivePresenter.
Open the approj file in a text editor like notepad.
Search for <mathml
Now look for your units (e.g. cm)
Here is how they will likely look: <mi>c</mi><mi>m</mi>
.
The problem is that each letter is being treated like a variable and single letter variables in mathml are always represented in italics.
A simple fix is to make it all one variable: <mi>cm</mi>
.
Alternatively, make it regular text: <mtext>cm</mtext>
.
Save the file, again being VERY CAREFUL not to change anything else.
Hope this helps!
Keith