Custom system fonts - Text gets very big after adding to card (Bug?)

Hello,

Thank you very much for this great work! But I have a problem with the tool.
I want to add some system fonts so customers can use their favorite one (Like Arial, Comic Sans MS etc). But if I use system fonts in the customizer and add the custom design to the card, the texts get very big (see the attached screenshots).

Google fonts work fine but I need some standard fonts like Arial, Comic Sans MS etc. My input is: Arial, Comic Sans MS

Version: 3.03

Tested with WP versions: 4.4.2 and 5.0

Also already reinstalled the FPD.

Many thanks for this great work and thanks in advance!