we have raised some issues in post 12921. unfortunately the issue still persist for us.
Please use sample.ppt, demo.docx. and sample.xlsx provided in your sample.
issues found in Groupdocs sample document are:
sample.ppt : Font colour turns to black for first slide, zooming incorrect.(UseFitToWidth = true).
demo.docx: High-lighted mark, font background incorrect.
sample.xlsx: Font colour black while actual colour is red.
PFA for screenshot.
Please let us know if there is some specific setting which we do need to set according to v3.4