So while in the Koranyon, Upper level, if you go through the Sturdy Wooden Door which leads to Mount Sarrunabi, if you equip a custom spell, it simply crashes. With normal spells it did not crash, only some custom spells. Simply equipping the spell or trying to cast the spell, it freezes and crashes.

Additional info:
Using OpenMW 0.49

The custom spell that I used to cause the crash:

Dissi's Greater Fireball
Fire Damage 100pts for 3 secs in 50 ft on Target

Here's also a video where I showcase this:
https://www.youtube.com/watch?v=-us-S9sSpMQ