It would seem the monster function crashes(clicking 'ok' you continue to run the program,however the bad function never runs again .i.e. monster_code)) , however the loop inside ent_movepath is still running. The ent_animate is in the monster loop that has crashed, so stops running.

Anyway good luck have fun. I got no answers for you, there is a reason that I don't use that function. Also i see the " ....." and there have been times your issues were with code inside the "...."
Track down you e1513, also that function - the monster will always "wrap" to the first node.