I don't use drafts. Generally, when I encounter a problem the first thing I do is Clear cache, cookies etc. Then try to use a different browser. If this does not help, hope someone with specific knowledge about this issue answer will.
Just to test the system, I went to one of my listings, used Sell similar and saved it as a draft. Then resumed the draft, everything was there. I use firefox. It may well be that this is specific to your computer/browser