Voldemort_5

Me and my friend have a world, in which a few villagers have their own houses. There's a fence surrounding them, so I know they're not escaping. They simply vanish into thin air when we're not paying any attention. Are they despawning, and if so, why? If not, what's causing this? Either way, I'd like to stop this from happening. Some have had good trades, like 3 fish for an emerald. Thank you in advance! EDIT: Also, this isn't necessarily a server. Rather, it's a LAN world.

So for whatever reason, on Tekkit Lite (and ONLY Tekkit Lite), whenever I do something such as farm sugar cane, the blocks won't update. This wouldn't be a problem if it didn't affect water and lava. Problems that occur look something like this: Thanks in advance if you can help.