ACF 5.6 Strange Tab Issue with Text Modus

[rogerburkhard]

Hey! Thanks for this great plugin - I use it very regularly.

Since ACF Version 5.6 I have a strange behavior. It seems that since ACF 5.6 all the Wysiwig Textfields are loaded in Text Modus instead of the Visual Wysiwig Modus. Even when I switch the modus and save the article. After the refresh I'm back in the Text Modus.

This:

Instead of this:

When I roll back the plugin to ACF Version 5.5.14 the problem doesn't exist. If you could look into this it would be a great help as I currently can't update the ACF Versions.

Thanks a lot.