Hello Lauren, I am wondering if you ever found a solution to your shifting footage. I am having the same issue. I am using a 2.7K timeline with 2.7K footage and 4k footage. I am nesting the 4K footage so I can use the warp stabilizer effect. Everything is fine like you said in playback and then when I render, it jumps down and to the left. However, When I switch to a 4k timeline the problem is resolved, the only issue being now that I have had to scale up my 2.7K which leaves me with a lower resolution than downscaling the 4K to the 2.7K timeline. Ahhhhhh, HELP!!!