So I've noticed that AI can randomly teleport to speed things up, or they can lag behind and not do anything. Are there any consistent strategies or is it just random?

They teleport because you went to a checkpoint and not doing anything is because they are stupid. Take for example Dom, he refuses to revive you sometimes like in Gears 2.

So what about when you kill the first seeder and kim can sometimes randomly teleport to the door? Is it a distance thing?

That is RNG, him and Cole can sometimes be fast to warp or take a while.