I think your problem is not so much a machine problem, but the fact that the test indicator was never design to be successively slammed like this test does to it. Slowing down as you have noticed is going to cure the problem.
You also mentioned some cornering issues, if this machine was built in 97 it probably -5 control boards, and if memory serves 100 IPM is approaching the max this machine can handle, my guess is if you slow your feeds down to 80 to 90 IPM most of your issues will go away.