Forum editor ignores edit attempts

The Forum editor has started ignoring Comment and Reply edits, perhaps as a result of the changes which added the "Drop files here, or browse" option below the editor window. The first post in a topic seems OK, but later Comments cannot be edited. By that I mean the Forum editor works fine for me while creating a new message, but after that message is Posted when I click the Edit option on the triple-dot "menu" and try to revise the message "Failed to update" pops up and the edits I made to that existing, posted message are discarded.
 
Tested in Firefox, Chrome, and Edge. I can edit, but when I click 'Post' the edits disappear and the post reverts to what is was before the edit was attempted. The only way I can 'edit' is by copying the original into a new Comment, making my changes, posting the new Comment, and then deleting the original post. 

Could this be fixed please?

ETA: Clarify that "edit" means an attempt to modify a previously posted message.

Please be aware that there are 2 kinds of responses in this Forum: Replies and Comments. When you Comment on a post by scrolling down to "Comment on this post here...", I am notified of your response. But if you select Reply, I am NOT notified and may not be aware of your response.