this hasn't happened to me nor anyone else so far, so I can't say what would be causing it specifically.
did you have just this mod on or others?
also, I'm sure you did, but just in case, roll back the server and see if it happens again?

I do have other mods active, but I can't think of any that would cause a conflict. I did uninstal the mod and the server ran perfectly again

very odd, it shouldn't be doing that.
I'll have a gander, not sure if I'll find anything useful though.

Allright, here's a list of all mods currently on the server

Ark Futurism, Monster Ark Hunting Evolved, Sevens Tranq Kit, Freestanding Oil pump, Midevial, Fog Remover.

The only thing I could see causing a conflit is the Monster Ark, but you both have custom creatures, so not sure how they could conflict.

I have this mod and a total of 29 mods on my server, all are working fine.

Great...that doesn't help us narrow down what could have caused the conflict/crash :/

Its causing my game to crash as well, i have none of those mods, but i am running almost 40 mods that worked perfect before adding this one in... i noticed its the lightning one thats bugged with this mod and the fire breath. i got near lightning and server crashed twice the same thing happened, then i breathed fire and crashed. but the alphas plus mod wyverns work just fine on my server for fire and lightning.

that is odd, maybe something is conflicting with the lightning dragon and firebreath in some way, either a file named the same or something. I've seen dragon deaths bug up a bit because of some funky things happening with the corpses, but I've yet to get it to crash.

while we have "custom" creatures, files may still have the same names, unless people are using something, for example, "megaawesomebreathofdestruction" as the name of their fire breath instead of just "fire breath".

However, I have no idea why only you two seem to be crashing in such ways. :(

Actually come to think of it, It may be fire as well for me. I spawned a Fire one in, but he breathed fire just fine, complete freedom of movement, and then about 5 minutes later it just randomly shut down the server

Oh well, sometimes it doesn't have to make sense, it just kinda happens. I've had this before with a couple of mods, no warning or reason, but they just refused to work for a couple of players while everyone else was fine.