I'm trying to update product variant related data via import. However it seems that I cannot make any data updates via import. Even if I try to import just one line of data with ID and some simple data field (for example standard price), I always get "Unclassified error: Information : <class 'IndexError'>: tuple index out of range at row 2". I have checked that the ID of the product I'm trying to update is in product.product database, as I have just prior exported it from the system.
If I just try to create a new product by importing a product name and standard price this does work.
Any thoughts how I could solve this? Any help is greatly appreciated.