Does it move one copy of the item, or none at all?

this is likely a mobile site bug, there are lots of javascript issues on the mobile site :/

as a temporary workaround, are you able to expand the list? like, if you tap the little + next to the item name, does it show you all of the individual rows underneath it for each instance of the item? if so, you can use those radio buttons to move the items for sure!

Did the above help?