I am experiencing this problem as well. I don’t see it in regular posts and pages, but it is happening when I try to edit WooCommerce product descriptions.
When going to edit a product category description, if the editor for the description starts on the visual tab, the text of the description does not appear. If the editor stars on the text tab, the text is there, however, if I switch to the visual tab, it disappears.
After the text has disappeared, the text is still missing when switching back to the text tab. If I switch back and forth between tabs again, the text entry box disappears.