Copy Sale Order as Return Order, Unit Selling Price is changed and Order Total more than original sa

Hi,

In case copy Sale Order as Return Order

Reproduce issue step :

1. Sale Order No.6002262271 is created by import Sale Order

2. Copy Sale Order No.6002262271 as Return Order

3. Choose Line Pricing as At Original Selling Price while copy sale order

4. Return Order no. 2000493958 is created and Calculate Price Flag is changed to PARTIAL PRICE

5. I do not change anything. Just hit Book Order button

6. After that I saw Unit Selling Price is changed and Order Total more than original sale order

My question is this case normal or abnormal?

I don't want system auto change Unit Selling Price. This is because it makes credit memo more than invoice that it is incorrect.