I have the same issue. I sent a support ticket in.
This is able to be reproduced by following these steps:
1 – select any page that has a normal WP content editor and switch the tab to “Text”
2 – leave that page by selecting pages (this seems to be important, maybe preference is set)
3 – select a page that has an ACF WYSIWYG editor and notice that it’s text editor, but without any buttons. It’s basically the “html” modal that pops up when you click the html button in ACF’s WYSIWYG full editor.