Hmmm, maybe disable the unicode sef? I think it has something todo with your SEF.
Thank you for the reply, it was not that
I found it... take a look at the attachment. All the products that have the URL field completed in "product information" tab show that behaviour. It seems like the URL input override the category id? Anyway if I delete the URL field, category id returns ok and back to category button works as it should. If this does not happen only to me, take it into consideration for the next update
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