will attach a test document showing imported pivot table with missing data field with grouped data, additionally sometimes even when such group fields are imported then the grouping data sometimes is corrupted ( see, document https://bugs.freedesktop.org/attachment.cgi?id=56181 attached to issue #45266 )
working on this, assigning to myself
Created attachment 56182 [details] test document showing missing field
fixed master:16af091a3339f6d00fe273f9dc5f155126e58881