Cause of chain ratcheting issues

[Monochron]

I am trying to determine the reason that the chain that lifts our elevator now skips on our sprocket when simply running the elevator stages up and down.

We are making some improvements to our robot in preparation for an off-season event and when we got to the point of re-testing our elevator, the chain started skipping. We physically can't lift a single RC more than a couple inches.
We have a two stage cascade elevator; the first stage is lifted by a chain, and the second stage is lifted by a run of steel cable. We are using #35 chain, 15 tooth sprockets, and the distance between sprockets is roughly 3.5'. Pictures of the chain can be seen in these albums:
http://imgur.com/a/uCo9b
http://imgur.com/a/34fYz
I tried to get it from as many angles as possible.

Things I have thought to look at:

1. Chain tention
   • From what I can tell, tension is just fine. Here is a picture of the chain at rest, and here is a picture of me flexing the chain as much as my hand was capable.
2. Chain misalignment
   • I can see some slight misalignment on the bottom sprocket, though (to me at least) it doesn't seem like enough to cause the constant ratcheting that we are seeing. You can see for yourself here.
3. Additional load
   • This is possible because we had to change out our top pulley holding the steel cable due to binding, and the new solution seem to be binding a bit as well. Even with this though, the physical force it takes to lift the elevator with your hands doesn't seem drastically more than it did in April. In April we never ratcheted the chain as long as our chain was tensioned.
4. Elevator stages "loosening"
   • The rectangular tubing making up the elevator stages has "loosened" a bit over time so the stage rocks inside it's parent stage a bit more than it used to.
5. Flexing sprocket mount (ie. c-c distance changing)
   • I don't believe that this is happening. The VersaPlanetary attached to the bottom sprocket is mounted very securely. I can look into this though.

That is what I have looked into so far, does anyone have any ideas as to causes for this? I am assuming that there are multiple causes for this, but some expertise in isolating those causes would really help us out. Any suggestions for things to look into or modifications to make would be great. As it is now we can't really compete