I took a look at the source code of Field Group and there is lots of stuff which we should fix. Take a look at this.
Just tracking work, I guess that I should create a new sandbox for that to re-test it.
Everything is in my sandbox now :)
No time to continue working on it :/
If having this error and having item active no selected and accordion error you can change field_group.js line 71
Replace this -> $firstErrorItem = $(this).parent().accordion("activate" , i);
with this -> $firstErrorItem = $(this).parent().accordion("option", "active", i);
Hope this help someone else time.
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