Orange skin display issues with Edge Legacy - home page gap; topic content missing

Hello,

Our clients have recently informed us of several display issues when using the legacy version of Microsoft Edge (non-Chromium). We have created output using the Orange skin. I have tested and confirmed all these issues by creating a new, blank project, using an unmodified Orange skin, and observing the results.

The issues are as follows:

1. The Home page displays a large gap between the drilldown tils at the top and any content you select for the home page
   • This appears to be due to an incorrect "calc" in layout.css that Legacy Edge interprets incorrectly. In Chrome and FF, it correctly shows as 100% - 29em. Legacy Edge shows it as -29em + 100%
2. The home page footer displays in the middle of the linked topic content, likely due to #1
3. Content on topic pages does not display. Only the breadcrumb headres for the topic show. This only occurs on a web server environtment; this works as expected locally.

I have noticed that the console in Edge Legacy reports errors with the opening XML tags from RoboHelp, where it considers the question mark in the <?XML tag to be incorrect formatting.

Any guidance on how to resolve these issues would be appreciated. These issues seem new since we upgraded to RoboHelp 2020; we did not have reproted issues in Edge Legacy with RoboHelp 2019.

Please see screenshots attached. 

Topic page local

Topic page on server

Large gap between tiles and front page content