Myzul isle or just undersea ruins in general?
Did you try typing //lua u xipivot to see if it still happens
Hard to tell, as I haven't run a Nyzul Isle yet since coming back; working on other things.
But yes, I had to fully unload XIVPivot just to proceed, so it's definitely something with the .dats in that pack (I attempted each three times just to be sure it wasn't some random crash -- identical symptoms each time). Whether it's related to those two missions only or Nyzul Isle instance style areas as a whole I'm not sure yet. I can't imagine it is, otherwise I imagine others would have mentioned it to Logical by now -- I haven't yet since I'm running the HD mods as well as Remapster, but I can't imagine the ingame map would crash in such a function and actual alter NPC nametext.
Though also interesting I've not heard about this from other people.
I did recently just finish a mule's run through ToAU last night, and same issue as I forgot to unload XIPivot. This was after wiping out XIVPivot and starting with a fresh copy.
I thought it might be that Nyzul Isle lamp .dat that crashes, but there's nothing for 0-240-111 so it's not that.