A bent bit could give the same readouts and I've personally seen several long flush trim bits that vibrated badly no matter which router they were in. Try the bit in another outer if you have one. Or try another bit from a different manufacturer in the same router.
It could also be some debris in between the tapered grip and the tapered hole causing the assembly to not lock down in line with the shaft.
Precision Bits makes a much improved and far more precise collet for the Colts. They include emphasis on keeping that socket clean, and the tools you need to clean it with.