Server randomly crashes very suddenly. It says in the stack trace that it's a NPE on a ticking entity, and in the entity's info, it lists its vehicle as "~_ERROR~ NullPointerException: null". I have crash logs from four instances - in every single instance, at the reported world + coordinate of the entity in question, there is a nether portal. I believe it is definitely something to do with retrieving their vehicle while going through portals.

[Stack trace 1](http://pastebin.com/g6yg0vyE)
[Stack trace 2](http://pastebin.com/eCBWdJHj)
[Stack trace 3](http://pastebin.com/Ang5eHkY)
[Stack trace 4](http://pastebin.com/rMjLQx4L)

[My plugins](https://gyazo.com/4da00240c6077e69233c0b801b98b866). It very well could be related to Multiverse Nether Portals being installed. I've done a manual command using that plugin to force all of my worlds to link up properly (those worlds were already linked properly for players, but maybe it was breaking something with other entities). If this solves my issue I'll report back here.