I have found a next issue when we save Visio as HTML. Here you have a sample project:
VisioTest.zip (52.3 KB)
Steps to reproduce:
Open project in VS and run it
Choose a destination folder and press the button
In the destination folder you will find html representation of the visio file. Left and right edges are cut
image.png (13.6 KB)
If you need more info, please let me know.