The bug:

Baisically, Ravages have a hard time pathfinding when being ridden by a mob.

Ravagers without a rider make a straight, fast beeline for their target. Ravagers with one will have a hard time: changing directions often, waving their head all around, spinning in circles, and overall being a lot slower and dumber than ones without a mount.

 Screenshots:

Pic 1: Both Ravagers can move in their pins to face their target, but the one with a rider is having issues turning its body.

Pic 2-3: The Ravager with a rider exhibits odd behavior 

Pic 4: The Ravager without a rider charges straightforward.

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 (See the attachments as the images for some reason displayed too large)

Update:

This bug still exists, but it's now different. The circling and inability to move forward has mostly been fixed, but now they turn there bodies a little when charging things and still can move their heads in really weird positions. One turned its head completely backwards to look at what I assume is its rider.