Which version are you using? I already pointed out this problems months ago… exactly the same as you, look…
Fortunately I have just a few multiple items listings, but every time they expired, the relisting sets quantity to zero and so they don’t relist at all. It’s months I don’t list multiple listings so I don’t know if this problem is only related to those listings you created with a beta (or very old) version of if it still exists also for newly created ones… anyway, I have those 5-6 listings that every time they expire I have to manually change the quantity… I told about this months ago, I don’t know where that listings went…
found Some new bugs and problems - #3 by fedege96 look, since January I still have troubles with the same listing!!