I’m having this issue too, and my theme setup heavily relies on patterns with ACF.
To overcome that critical problem right after updating WP to 6.8 I was using Gutenberg 19.4 from official github repo (last version before Gutenberg forced iframes in patterns) – before release of ACF 6.4.1.
The workaround I use for now: very simple plugin (uses only jQuery from core WP) to easily drag and resize right sidebar of Gutenberg – then you can edit fields without frustration. Not perfect solution, but way better than having to fight with tiny fixed sidebar.
https://wordpress.org/plugins/resizable-editor-sidebar/
I hope ACF team will find perfect way to overcome problem.
