hyper v2 whining

well half way through a tattoo my v2 starts making a weird whining sound. The performance doesn't change at all. The machine is well oiled and kept in like new condition. After the tattoo was done I cleaned and re-oiled it just in case. Still the same whining. I don't know if its coming from the motor or the bearings or what ever else. I did however notice my stay up spring wasn't doing its job, but was perfectly fine on my last tattoo. Any ideas? I'm going to do a full breakdown tomorrow to pin point the problem and I'll post results in case any one else has this issue in the future.