When using Select Advanced filed, position of the dropdown is invalid in the front-end forms, both when it appears above or below the selection container, and seems to be affected by the WP admin bar height: The jQuery(document.body).offset() in the console is the same as the admin bar height, and Select Advanced by default uses the body attachment.
To add context, the Select Advanced field has 'multiple' => true and is included within Tab.
I have also checked another field that accepts only single values and is not included in a Tab, and then the dropdown is displaying correctly below, but the issue still exists when the dropdown appears above the selection container.
You are right, the WP admin bar affected the position of the select box. I've escalated this issue to the development team to fix it in the next update.
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