Anytime I enter/exit a Nether Portal, the dogs will get up on their own, and I'm unable to order them to sit unless I restart that world.
Notable: Now that I think about it, the first obsidian block had a sign next to it. (I thought signs weren't flammable via lava?). This stone block has a wooden door next to it. The video showed a wooden bridge next to the stone catching fire...perhaps this is the cause?
Here you go. The block itself wasn't on fire at the time of the crash.
As you can see in the screenshot, a "lit up" lamp can be seen after being harvested with a Silk Touch tool.
I had tried to get an enderball onto the ladder, and ended up moving the mouse at the last second, hitting the wool wall instead. I suffocated inside the wool before I could get out.
When trying to duplicate this on Bandicam, however, I never once wound up inside the blocks.
This is a multiplayer server.
On my SMP server running 1.8.8 vanilla, 7 of every 9 (so far) named slimes have despawned.