Slot order with Handbook Articles can cause issues in Firefox.
The issue appears in Firefox, where the pdf slot appears way over to the right of the page. The cause is a result of the slot order on the article. Here is what it looks like when the slot order causes problems in Firefox:
The slot order in this case is: pdf/file slot first then text slot as seen here:
By simply reordering the slots, the issue is resolved. Here the slot order is changed, with the text slot at the top of the page:
And the issue in Firefox goes away: