602 Balancer question

I have a friend who runs in a 602 only crate class and he just put the 3rd harmonic balancer on his 602. Twice, the outer ring walked ahead until it touched the water pump pulley and just last night, a brand new balancer had the outer ring go back and start touching the timing cover. He has 3 cars with these motors and it isn't always the same engine doing it. Any ideas out there??? Is there an aftermaket balancer that is the same size, weight, balance, etc. to the stock one available? He just paid $136 from the local GM dealer for the last one so he is a little frustrated. Thanks in advance for your ideas..........

How many RPM is he turning it?

They have to run a rev limiter with a 6200 chip. Normally, it just starts to sputter before the end of the straightaway.

What is the part number of the Harmonic Balancer he is buying?

Is he running the crate flywheel on the back that is weighted or neutral flywheel?

When he installs the flywheel he is not using a hammer on it is he. Those cast dampers are sensitive to whacking on them, especially if you miss and hit off center of the main hub, they really need to be installed with a screw-on type installer.

Without more information it is hard to go further with the trouble shooting.

Are these engines stock or re-built?