Update Merchant issues

Using icodes, I have been trying to update my merchants via the icodes import tool plugin… While it seems to update the new merchants and pulls them in, previous merchants suddenly loose their Category and Store ino in the drop-down fields.

I then spent ages to trawl through them to get them re-set only to find that on some of the merchants their Store field is blank, whereas others are showing the complete list?

I appreciate any help you may have.