Optimizer Plot Test - Magenta Cast in Optimizer Head test

Hi, Hope you can help please We have 5 Latex printers, and are aware of the Magenta cast issue on Greys On one of our machines, Printer #2 , when we do a Plot test, to check the heads, we see what looks like a perfect plot test. No breaks in the lines or grids, solid colours around the head numbers. However, in the Optimizer Head 1 test pattern, instead of the test looking almost black or a very very dark blue/black, the Optimizer plot test on head 1, seems to have 2 magenta coloured thick pillars in the test plot. Not seen this on any other machines, but this machine leans towards magenta at the best of times, but noticed this in the head test. Please see the attachment any help or advice, appreciated thanks in advance Jack