Toolsmith trade menu keeps closing immediately after opening it

I've been sporadically having trouble with the trade menus of villagers closing immediately after I open them.  Right now, it's a toolsmith, the only one in the village.  It was a leatherworker yesterday (and I don't think the toolsmith changed jobs, I leveled him up a bit).  When I right-click on the villager, the menu opens, but closes within about 0.5 seconds.  It's not a mouse issue, as I can open the other villager trade menus just fine.  Nothing I do seems to help.

On a related note, I've been using beds religiously to avoid sundown mobs, but my villager count went from 8 with a child to 5 without the child overnight.  I lost both farmers, the child and a leatherworker.  The bell did not summon them, either.  I don't understand how villagers can just disappear when there's no hostile mobs around to kill them.  I've been trying to grow the village, and problems like this (I'm assuming it's a bug at this point) are very frustrating.  I have all the job items in the village, but I can't get villagers to spawn so I can get an armorsmith and weaponsmith, much less farmers who I can trade spare produce to for emeralds.  The bell needs to magically summon ALL villagers belonging to that village, to the center of the village, from ANY distance - that can rule out random disappearances.  If villagers are just disappearing for no reason, villages are a complete waste of time, because I can't keep the villagers I need to build up an emerald stockpile so that I can trade for diamond products later.