That is exactly what is happening to me. It seems like (but I am not 100% sure) that if I start a new listing and then sell similar from that listing everything works as planned.
If I go into my saved listings to sell similar (I click on the icon on the right side that brings up the old info which I can then modify), then I have the problem described above.
I plan to list a lot today so I will see if this theory works out.