Wordpress - Editor Page loading page missing content

I've searched everywhere, but I always find other subjects related to the keywords used and never my case.

I have a WordPress website and when I edit my homepage, publish it and try to edit it again, WordPress doesn't load the whole content of the page in the page editor. But this usually happens when I put a large amount of content on the page. And if I save this partially loaded page, edit it and publish again, the page is saved the same way it was loaded, missing content (and I lose it all forever).

I have tried to change the name of my plugins folder temporarily (to find out if a plugin was crashing something), but nothing changed. I raised my wp memory limit to 128MB (+-) and max_input_vars to 5000, but nothing solved. At first, I thought it was the max_input_vars, but...

I program to Android and games, not web backend. I'm making the site only through the wp-admin page from a WordPress theme.

How do I stop losing these contents?? Thanks!