Unexpected header font size

Hi,

I’m planning to use the Theme “Hive” (Pro) for my Blog and copied it for testing to a local XAMPP installation.
When I install the recommended Plugin “Customify” the font size of the headers get unexpected small on some screen sizes. This is happening when viewing a post.
I found out that on some screen sizes the font-size for h1 is 3.38px while on other screen resolutions it is 3.38em.
In “Appearance” -> “Customize” -> “Theme Options” -> “Main Content” -> “Heading Fonts” -> “Heading 1” I can set the font size (at the moment “3.38” is set).
But I don’t know how I can prevent that the size unit is switching from “em” to “px” for some screen resolutions.

I’m not sure if this is a “Customify” problem. When disable “Customify” then the font sizes are well in all screen resolutions. But of course I lose all other settings I have made with Customify …

Best regards,

Stefan