I found in my level that waypoints didn't work, so I got annoyed and deleted them all..
I thought it was just me, maybe its a returning bug. I get a lot of my AI trying to run through walls again.
For me I thought it might be because the waypoints were too close to things. E.g. entities on the ground etc.
Custom Mac Pro (2014): OSX 10.10 (Yosemite) and Windows 8.1 Pro:
Octa-threaded Xeon E5 v2 @ 3.7Ghz [9775]; Dual AMD FirePro D500 (3GB VRAM Each) [3769]; 12GB RAM [2517]; 512GB SSD [9074];