can no longer scroll workflowy in Firefox's sidebar

Issue: I am no longer able to scroll workflowy when opening it in Firefox's sidebar.

Explanation: I often use the "sidebar" on Firefox to keep certain websites in a persistent "split view" while researching/browsing. Examples include; twitter, raindrop.io, native bookmarks & password managers. However, the scrolling issue is only present with workflowy and has only arisen within the last week.

This might not be a workflowy "bug" - but despite attempting various fixes - such as editing the userChrome.css file - I am stumped.

Any help would be greatly appreciated, many thanks.