Sales price

Hi,
I have this problem on PRO add-on:
– If I have sale price set on a product (both regular&sale price set) and I try to remove sale price for a product (to get default woocommerce behavior : regular price set and sale price empty), I can’t get it to work (to obtain a empty sale price box in Back Office).
I try this setup in excel file:
– regular price set – sale price empty and I get on woocommerce frontend sale price = regular price and regular price strikethrough;
– regular price set – sale price 0 and I get sale price 0 and strikethrough settled regular price
– regular price = sale price (this way I get what I want – but in BO of woo, I still see sale price setled and = with regular price )

How can I get a empty sale price box in BO?
Thank you!