Problem updating Prices


I was wondering if someone else is having the following problem:

I wanted to create a price list for this new year, so I opened a list with all sales prices corresponding to last year, and as I wanted to review some of the details of the products, I opened each price, duplicated it, and updated prices and other details (units). After the 100 first prices, I reviewed what I had done, and some prices are duplicated on last year price list.

The problem is that when I open the duplicated prices, and try to change the price list they belong to, it is impossible, and they always return to Standard Sale price list that is the list that I was using last year.

I am using last v12 version in production mode last updated this morning.

Many thanks and kind regards from Spain,