Data upgrade problem on price sets

I have been getting some odd results on a recently upgraded customer & have found some data issues that appeared after the upgrade. Several line items have been created for each of their non price-set membership contributions.

This customer is unusual in that they had multiple membership price sets in place prior to the upgrade so that

SELECT * FROM civicrm_price_field_value WHERE membership_type_id = 7

Returns 7 rows including one for the new default membership price set. On upgrade every membership of this type that was not already linked to a price set id had 7 rows added to the line item table for the relevant contribution and the total of those rows is 7 times as much as the contribution.

I don't necessarily think that it's worth doing anything to tidy up data on already-upgraded & affected customers - but I do think there will be a fairly obvious SQL fix somewhere in the upgrade script.