Still vexing me . Problem had gone away it seemed , now it has returned . Prints look light , will sometimes stop mid run and idle , stopped at one point and said toner supply failed , checked both toner drive and doors on toner and developer unit , all looks fine . Checked toner add motor with toner out thru diagnostics , seems to be turning fine . Also ran sims for toner sensor and toner dispenser motor together with toner in machine , showed toner sensor at from 2 volts to 2.5 v , jumped around there , not sure what normal should be as manual does not say . FW Main controller is at 2.50.05.08 . I am leaning toward trying a new Imaging Unit as all else seems fine . Also was thinking firmware , as possibly old Firmware has become corrupted in some way , but I am not sure if it needs the old Firmware for older computers , not sure what customer has or if it matters . Maybe try a system restore/reset ?