When exiting the Nether through a portal, I tried to mine some nearby nether rack just because (had an iron sword in hand). I also had a few cats following me, if this is important. When the teleport was supposed to initiate, my game crashed. No important data or adverse effects appeared, but it was a little bit annoying to have to launch Minecraft again. You may be able to replicate it if you mine blocks while teleporting. It may have been caused by another factor, but mining white portalling was the most obvious issue that I could think of.