Track to bone constraints lag behind animation/don't update correctly

Question

I am trying to make an animation for a friend that involves a robots arms that move together and a third arm attached rotates with the arm on hinges:

The second arm copies the rotation of the first and the third is parented to the first. There is an empty parented to the second, and the third arm always points to the empty.

When rotating the arms or moving the armature at all the constraints lag behind and don't fix until updated.

This wouldn't be a problem if the issue were exclusive to the viewport, but when rendered, it fails to update the armature per frame and still lags behind.

Does anybody know a fix/solution to this issue, the project deadline is in a few days and I'd be very appreciative of any help.

Answer 1

Idk if I got your setup, but imho you can do something like that with 2 armatures:

A first one-bone armature, and an empty parented to it (tip of the bone)

then another 2-bones armature, where each bone has different constraints: the bottom bone copies rotation of first armature bone

and the horizontal bone tracks the empty

to show it working, I parented 3 cylinders each to its bone, and key framed rotation of first armature only

in viewport:

and rendered:

gif timing seems weird but I rendered to h264 avi and it works really well, no lagging

here the .blend