Quite annoyingly, after saving a page, and sometimes, sometimes not, the page turned empty. White. Blank.
After much research and ado (hours!!) I found out that I had a blank line in functions.php at the end, after the ?>
After removing the blank line everything worked again.
I’m not a PHP guy, just using wordpress. I think that’s a major fuckup. But anyways. Delete the blank line after the last ?> and everything should be just fine.