Appears to be a missed cut n paste :)
This also effects D7.14
The patch in the issue summary applied cleanly with an offset and removed the unnecessary "collapsible" and "collapsed" properties which should only be used with fieldsets (not textfields, or form items inside of a vertical tab).
Oops. :) Nice find!
Committed and pushed to 8.x, though this didn't seem to apply to 7.x so moving to backport.
Backport of the patch in the original issue summary.
Guess I can mark this as ready since someone else rolled it :)
Committed and pushed to 7.x.
Automatically closed -- issue fixed for 2 weeks with no activity.
This issue has no child issues.
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