AI Characters disappear at far distance, need to keep them visable

In the game we are making we have many large AI characters that need to be seen at a far distance, due to the large open level design. At the moment while playing in the game if we back up to a certain distance the AI will become not visible and then if you walk forward they become visible again, as if there is an invisible trigger volume for their rendering or something like that.

We are trying to figure out how to increase this (what appears to be some kind of culling) to allow for the player to see the AI from a greater distance.

We have tried increasing the max draw distance and that so far has had no effect, have also tried disabling allow culling volumes and it also had no effect.