How do I revise item using the advanced tool ?

I have an item with a bid, I need to ad some extra info and with the new selling/edit tool I always get this message :

 

"We're sorry, but we lost some of the information you entered. Please go back and re-enter this missing information"

 

I dont want to end the item and relist as I may lose that bid.

 

I prefer the old selling tool MUCH better !

 

Thanks.