We are aware of this issue and it appears to be caused by having an older version of the Lato font installed on your machine. You can work- around this issue by either uninstalling the Lato font or by installing the most recent version from here: http://www.latofonts.com/lato-free-fonts/#download
I have played around with one idea but it is far away from being perfect:
Create a formula that is eclipsing all previous formulas in your matrix. In this example, the formula is:
Product = IF(Month[THIS]= 0, “-“,Month[THIS])
The issue is that it is involved in one more circular references what might be an issue.
I have attached the sample file.
As I said, not the perfect solution but perhaps a base for better ideas.
Another idea is to use color coding with conditional formating.