The upc field is invalid error when i update a price of item

[CutCosmetics]

Hello
In a function it is done the update of the prices by the following queries:
...
$ QueryUpdate = "UPDATE` "._DB_PREFIX _." Product` SET price = $ newprice where id_product = $ id_prodcut ";
$ UpdateProductShop = "UPDATE` "._DB_PREFIX _." Product_shop "SET price = $ newprice where id_product = $ id_prodcut";
Db :: getInstance () -> Execute ($ queryUpdate);
Db :: getInstance () -> Execute ($ updateProductShop);
...
The update is done but when I want to change the price manually the following error is displayed: The upc field is invalid.
How do I solve this problem? Thank you

[NemoPS]

What is the upc field set to?
I take it as saving from the first page (information) works?