It sounds like you’re using a field group with the “No Metabox” style. If you temporarily change the field group to use the standard WordPress metabox, you can then drag it out of the sidebar. Once it’s in the normal position, you can change the metabox option back.
I’ve experienced this many times – once you’ve loaded a page with a set of fields, the order and position of those fields is fixed, even if you try to change it in the ACF admin. You need to enable the metabox handles to drag and drop them into the order you want.
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