I am using Firefox 89.0 (the latest as of June 4, 2021) and one of my documents has developed a strange glitch. When I try to edit something involving a page break (in the first attachment, I was attempting to delete the page break between 'letter' and 'and') the document becomes unresponsive and I receive a "this page is slowing down firefox" bar just under my bookmarks. Until I either forcibly stop the process using task manager or close the tab manually, it will continuously increase RAM consumption, up to about 70% of my computer's capacity (8.5G of 12, visible in the second attachment). Creating a copy of the document did not fix it, nor did copy-pasting the plain text contents into an wholly new document. The full length of the document is 80 pages, in the original and first copy, but it does not always display as such at the bottom of the screen, jamming at 35 on the original and 28 on the copy-pasted version. I'm fairly certain it isn't the length, as I have a document nearly twice as long which has exhibited no such issues, but I'm out of ideas as to what could be causing the problem.