Thanks for the clarification. I was easily able to reproduce the behavior you described using a sample of auction format listings, and have forwarded the details of that issue over to our technical team for further investigation as well. The issue does appear to be specific to auction format listings as far as I am able to tell.
Unfortunately, this same behavior also seems to occur when using the “Bulk Edit” tool that is available on the old version of the Saved Listings page, and I do not know of a workaround to prevent this from happening under these circumstances.
I will let you know when we are able to address this issue, or any related information becomes available, as well. If you notice any remaining issues of this nature, please don't hesitate to let us know.