I'm not yet able to find a solid theoretical reason as to how this could happen, though I think SwitchingBundle::force_requests_to_complete() could be a candidate for breaking the sync...
1. Does VT switching trigger it or make it worse?
2. Using multiple monitors?
3. Do you find that like bug 1216472, the frames are disordered, or just lag?
I'm not yet able to find a solid theoretical reason as to how this could happen, though I think SwitchingBundle ::force_ requests_ to_complete( ) could be a candidate for breaking the sync...
1. Does VT switching trigger it or make it worse?
2. Using multiple monitors?
3. Do you find that like bug 1216472, the frames are disordered, or just lag?