In some cases Html2Canvas does not handle proper font alignment producing overlapping or squashed text.

Description

Html2Canvas does not always produce expected results when multiple fonts are used in CSS class parameters. In particular, this can result in overlapped text when scaling the image.

Workaround:

Include an optional app settings parameter that can be used to override the font used in preview mode. 
<appSettings>
...
<add key="EPiServer:Marketing:Testing:PreviewStyleOverride" value="font-family: 'Sans Serif'; background: grey; color: white; !important" />
...
<appSettings>