page not saving

Hi there,
I faced a serious problem with one page that was working for years now. When I tried to save some minor changes (like editing text) ALB was not able to save the page. It was trying to save endlessly – I had to give it up after 15 minutes.

What I tried to fix it:
1. I updated everything (WP 5.5, Enfold 4.7.6.3, PHP 7.3, all plugins up to date)
2. I increased the PHP Memory Limit (256MB was the Max my Hoster gave me)
3. I checked the code of the page for open or false markups

nothing worked out.

What helped (as a workarround):
Because this certain page accumulated much content over the last years (Text & Accordions with tables inside & Blog,…) AND it was changed very often I was wondering if the almost 500 revisions of the page may be the problem:

so what I did is:
1. I created a new (virgin) page
2. I coppied the CODE of the old page using Code-Editor
3. Pasted the code inside the new page and changed back to Visual Editor (ALB)
4. moved the OLD page to trash (not erasing it completely)
5. Changed the Title and the URL of the the NEW page (so that is linked correctly)

….that worked for me so far. Now everything is saving within seconds.
Could it be that there is a bug when saving a bigger page having many revisions??? I just was wondering why this was happening. I still kept the OLD page in the trashbin. See private content if you wanna have a look.