833 OD vibration

I called the shop that balanced the shaft for me and they said they only spun the shaft to 2500rpm. I took the shaft back and had them balance it again, but this time I specified that they spin the shaft over 3000 rpm. the guy tried to balanced it again, then called me when he was done. he said the shaft was balanced until it hit 2900 rpm, then it started going crazy and he couldn't balance it. now I am having a new shaft made.