Odd issue with Infiniium 54815A input impedance

[wastedhotdogs]

I recently purchased this scope and have replaced the CMOS battery, installed software version 4.3, and am now working on getting it to calibrate. Initially it passed all self test but would fail to calibrate all but one channel. I narrowed it down to the attenuators, as the calibration success followed the one attenuator as a swapped it between channels. I have taken the attenuators apart and cleaned and reworked the relay contact springs. I now have three out of four channels passing with a weird issue on channel 4. The calibration fails early in the process and I've found that the input impedance switching is inverted. It reads a near perfect 50ohms with set to 1M and a spot on 1M when set to 50. Has anyone encountered this?

[m k]

So one inverter in selection line is now a buffer.

Are there enough discrete components to check the selection line?