What appears to be a previously unreported bug. When fighting a monster in a vault, in 3.5.1, items dropped would "disappear" only if there were no available spot for them to drop. Now it appears that they "disappear" much more frequently, even though there are some available spots. Maybe it is dropping only one item in the available spots but not stacking? Maybe it is not dropping if it's original choice of drop point is unavailable (due to a trap, permanent wall, glyph, etc.) and is not seeking an alternate drop point, even if that involves stacking?
Patient.zip See the message history, (1) Qlzqqlzuup drops and "The Tulwar disappears". See several pages back up the history, the Knight Templar drops, and 13 items disappear. There were available spots for drops if the items could stack, but apparently they couldn't. (And before anyone asks, no, the ironman setting for don't stack objects is not on.)

EDIT: Confirmed it's a stacking issue, at least in part. Just dropped a ?Banishment to make room to pick up some items for pseudo-id and the scroll disappeared rather than stacking. Damnit! Also, just found the stacking issue is prevalent anywhere, not just in vaults.
FURTHER EDIT: This bug just keeps getting worse. Just read a ?Acquirement over an empty floor space, but the item disappeared. Is it because I squelched an item in that location earlier? This has become my new #1 frustrating bug.
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