@mikkor We have multiple sites that has the problem, and going back to classic editor plugin is a big hassle since our clients have been trained in Gutenberg now.
We have opened a ACF Pro support ticket, and if they cant help us out soon we have to install that plugin.
It seems it’s a TinyMCE bug since the issue was present is WP version 4.9.8 also
https://core.trac.wordpress.org/ticket/44911
I have also reported the bug there.
Lets hope we find a solution soon.
