It’s very nice that CSV import will try to find which rows have non-blank data, but it seems to get it wrong quite often. I imported a large CSV of our vendors and it missed half of the fields that actually had data in them. Actually it failed the import. For most of the fields that Fibery thought were empty, upon completing the import, the fields were in fact imported as empty in Fibery even though they do exist in the original CSV.
Ah, it turns out this happens when the field name is repeated (as it apparently is when doing an export from Sage Intacct). This seems like something Fibery could check for and detect.