Does this happen in the beginning of the game when NPCs haven't yet learned Dualshot / Multishot -talents? Does this happen only with NPCs that you have recruited?
Only with recruitables (I haven't gotten any trouble with summon room skeletons yet but they die pretty fast so I don't know about them; no trouble with tamed animals and other creatures without an inventory).
How do I check what talents they have (and would I get some notification when they learn it)? But likely without them because I only got to dungeon level 3 a few times so far (either I get a nice run that crashes as early as level 1, die trying to tame an elephant, or die to triggering something nasty while looking for recruits because at the moment I'm adamant on sticking to my frail commander build and the game is still very enjoyable despite not getting far).
The drow equip -thing: Did you try to equip a weapon from the right side of the inventory by pressing enter? From there you can only equip shields to the off-hand but if you switch to the left side of the inventory (equipment slots list), select the off-hand slot you should be able to equip a weapon if the character has the dualwield talent. If this doesn't work then it's a bug.
First I tried replacing both weapons by equipping from inventory but it was only swtiching the first/main one, then I tried equipping from the "equipped" column but nothing was showing on the list as possible to equip (he had no shield on him at the time), then I accidentally unequipped the off-hand sword, then I tried reequipping it both from inventory (which only switched the main-hand weapon) and from the equipped column, then I gave him a few shields and that was the only thing he could put there. If he's supposed to learn a talent for that eventually, then he probably didn't have it yet (I found him on either dungeon level 1 or 2), though he did have those two swords equipped by default when I found him.
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I had a quite lucky run with all sorts of recruits throwing themselves at me and I stocked them with various kinds of ammo. Recruits with multiple types of ammo were fine (including those that started without any ranged weapon and got one from me), and so was one drow (this one spawned with a sword and a large shield) that I gave an infinite arrow (I didn't find more of those). Also lucky because I got quite far without crashes. Eventually the drow died to an encounter with a naga in a chokepoint (together with most of my party except one elf with a mix of arrows) but later on that level (3rd) I found yet another elf, whom I gave that infinite arrow. Before that everything was fine with all sorts of missiles flying around (including the infinite arrow, and with recruits running out of ammo or switching to differently-enchanted arrows), but this time it crashed after a few battles:
Positioning behind the popup (not sure why the PC and mimic sprites disappeared after the popup showed):
The battle with the (chest) mimic initially started with the rest of the party off-screen and the crash happened when the elf (green one) saw the mimic. The other elf in the party was carrying normal enchanted arrows and didn't see the mimic yet. I don't recall whether the green elf shot at any point before that, but there was another battle against a mimic (door one) before that, albeit with ranged LoS blocked:
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If friendly mushrooms hit me with the poison cloud while targetting an enemy next to me, they turn hostile but their HP counters don't immediately turn red (so it's a turn or two of greens attacking me).
AoE clouds also seem to turn party members hostile to each other, like here I had one elf trigger a mercenary recruit from the teleport shop/level, which resulted in another party elf (not visible) joining the fight on the side of the first elf (while all three stayed friendly to me and other party members):
The mercenary had lots of fancy +3 items but eventually succumbed to the storm clouds. BTW is that OK that I got him through the shop on the first dungeon level, equipment included? He mostly single-handedly carried me to the third dungeon level, and that's with 100% exploration and killing everything that moved and didn't join me.
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Elves also can't resist the urge to equip chain armor they find on the ground if they're wearing anything else (usually happens because I just took it off them and dropped next to them, but it doesn't have to be theirs), even if their new elven chain armor is better, and even if they already have one in the inventory (the one in the inventory they seem to ignore / not auto-equip, but will drop it together with what they had equipped). Would it be possible to add some "force equip" command for the player to use that'd disable them trying to find a different equipment piece for a given slot?
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Love the amount of secret rooms within secret rooms and that items on the ground can spawn with a floor trap below them.
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Summoned mushroom people subconsciously knowing where the nearest mushroom field is is intentional?
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This summoning room summoned two friendly zombies and after that flipping the switch does nothing but is marked as active on the map (I tried removing already present corpses from the floor as per the floor message but not killing the summons I got, as so far summoning rooms could be used several with varying results and then the switch would disappear). WAD?