Pop cap

[Nekodar]

I've done Odin on a legacy server and never disconnected once and havn't heard of anyone else crashing during the fight either.

So it must be something wrong on your end if it only happened to you and a handful of other people.

Since you seem to be unaware, yes, some servers have crashed due to Odin and/or Behemoth. Does it happen on every server? No. Does it happen on many servers? No. Has it happened on some servers? Yes.
Chances are you'll never even see the pop cap in effect no matter how long you play.