I have been observing behavior in Audacity 2.0.6 in Win7 somewhat similar to the known issue documented in the release notes here:
However, I have found a somewhat more bizarre (UI?) bug that I thought I would describe.
To reproduce: Create a stereo track. Generate multiple 1sec contiguous tone clips (5-10 will suffice). Create a new empty track. In the first track only, select a contiguous region containing precisely all of the previously generated contiguous clips.
Now, a few different odd and inconsistent time-shift behaviors can be observed (occurs both with time-shift tool and multi-tool):
Dragging a clip from the left/top channel into the empty track will have strange behaviors somewhat corresponding to the bug described in the release notes. One channel of the dragged clip may move with the other channel of a non-dragged clip, or the clip may move alone, etc.
Dragging a clip from the right/bottom channel into the empty track will have quite variable effects depending on mouse position. Some parts of the selected region may move unpredictably, and more may arrive as the mouse position moves vertically or horizontally across the destination track. This behavior also seems unpredictably dependent on the exact source location of the dragging action.
Feature request 500 may also be relevant to this issue, however my two cents on the matter of what to do with dragging clips that span multiple tracks is to try and fit them (with relative timing intact) into the drag destination, and if there is overlap, to do nothing.