Exporting Products-doesn't show some products and images urls

I export my products to a csv on a monthly basis - in order to upload it back to the shopping comparison websites etc.

This time, it was exported, but for some of my products, it exported only title, price, code and quantity, and did not export the product url, image url, condition, weight etc.

I tried it a few times, and it keeps on happening on the same items - this didnt happen before. I checked the DB structure, and found that under product_type there is a variable “P” which I don’t know what it means. However, if I edit the description of the product, and then look back at the DB - the P variable is deleted and it’s empty.

Most of the products that do not have the url are ones with no “P” in the field.

Anyone suggestions?