When you've clicked Sell Similar& your listing opens up, don't you see under Variations near the top : Change Variations - Change Pictures - Remove All Variations ..?

I haven't actually tried it yet as I have to wait now til the listings I missed doing, fit in with some others coming around.

Otherwise if you don't have that option, try redoing an entirely new listing - have 2 windows open & copy from the broken one to the new page. I was relying on that to work!