WP 5.0.2.
Disable Gutenberg plugin is active
TinyMCE worked perfectly until recent update. Can’t say whether it is the WP or GP update, that caused the following flaw.
Now tinyMCE shows up correctly when editing pages & posts, but not when using sections.
Then buttons show up only partly – for example justify button, or select field font-size are missing. The tinyMCE editor drop-down menus are working, but this is an annoying solution. Have a lot of text-align:justify and with the drop-down menus it needs 3 clicks until done.