I have the same problem. But I doubt that this has anything to do with the IOS version specifically. The Android version has the same problem.
The object stability only works well for objects which are not too high in relation to the marker. If have an object is placed far away from the marker (or big in size), it will wobble massively. This is the case for both the frame markers and the image targets.
It is a deficiency of the tracking algorithm used. The tracking will always contain a certain amount of error. A small error in translation isn't so bad because it is hard to detect. But an error in rotation gets amplified as you get further away from the marker. This is what you are seeing.
String AR has this problem as well but it has far less wobble with large objects then QCAR. If you want to eliminate this problem, you have to use multiple markers spaced far apart (not on the same plane), bring them into a single coordinate system, and average the tracking matrix. That's just a theory though. I haven't tested it yet, but I am working on it.
Try the new version 1.0.6 for Android. The jitter is reduced. Not sure if this incorporated in the IOS version though...
You can find the Unified Coordinate project here: