We are facing a spurious spikes from only one radial probe (X) from NDE of Centrifugal compressor driven by a steam turbine. all other 7 probes are normal (y of this radial, x&y of compressor DE, X&Y of steam turbine DE and NDE) and no any abnormal process conditions existing. We made everything (replaced the probe, the extension cable, the SPD (surge Protection Device) and the proximitor). all replaced by new ones but problem still exist. extension cable is in a metallic conduit. we tried swapping the probe and extension cable together between X&Y and found the problem received in the Y channel of the 3500 BN monitor. so the problem now from the probe and extension cable only, but they are new and also in a conduit for noise immune. So any suggestions or ideas? Is there any mechanical issue on the compressor can cause such this scenario?