I dealt with a couple of seizures on my TZ, one was a proper good old fashioned crowd/marshal scatterer at Greeba Bridge before I got hold of the clutch, there's a specific part in Guy's crash footage just before he comes off where the forks/bars seem to wobble then get back in line - that's the very same actions movement etc and reactions involved when you feel it locking up as the back wheel comes round on you but then hopefully hopefully the situation gets marginally better when the clutch is grabbed and the wheels get back in line.