Hi, first of all I'd like to congratulate you for the incredible piece of work that is Morroblivion.
Straight to the point, I was doing a mission that required to go to Punabi so I went straight from Balmora but when I reached Nissintu the game became an slideshow, the drop in the framerate was incredible, passed that area everything went smooth again as if nothing happened.
I tried to lower the settings while in the area but to no avail, it became an slideshow whenever I passed through this (small) area.
Normally I can play Morroblivion smoothly with maxed settings.
I know it's not a big issue because the game doesn't crash and after moving out of there everything goes normal. It only happens in the surroundings of Nissintu (a small area) but not in similar terrain.
Regards and once again, congratulations.
Could be a trapped cliffracer
Could be a trapped cliffracer that was spawned incorrectly. This happened to me before but mostly in interiours. Try opening the console and typing killall or maybe tcl and look for any creatures that might be glichting out.