If you have an item with an item specific hold on it on one bib record and you use the 'attach item' function to move it to another bib record the hold does not transfer to the new bib record, but if the item was waiting the waiting note remains on the item. It sounds like the bibnumber isn't changing in the reserves table, and so the hold is listed on the wrong bib but the right item.
a derivative of this is when you move an item from one bib to another, and the item has a hold waiting, filling/completing the hold doesn't remove the reserve, because the reserve is still attached to the old biblionumber.
That is to say, I confirm this bug.
*** This bug has been marked as a duplicate of bug 8723 ***