K4 Problem after Kubricking: can't exit DIAG-pcbId and DSN don't match

I was trying to add custom screensavers to my K4 NT, and on discovering that you could no longer access ssh on firmware 4.1.1, via USB/ethernet, I ran the Kubrick wizard, as the sticky implied it would add a hack that enables ssh root access again.

Kubrick worked fine, and after the procedure I tried to add my own screensavers by accessing the Kindle via terminal on Mac and entering diag mode.

I ran commands to create a backup folder for the original Amazon screensavers, and to create a new folder for my own screensavers, basically as detailed here http://brettbuddin.us/log/13508573/c...4-screensavers

After completing the commands I tried to disable diagnostics mode from the Kindle menu, but it would not quit.

It said, when I entered 'disable diagnostics'

"pcbId does not match DSN

pcbID 0031707125023TW5

DSN 9023170225xxxxMB"

DSN was my device serial number unchanged (I have replaced some numbers with x's for anonymity).

I couldn't get any further, so to get out I had to run the entire Kubrick again!

Question: what does this mean? will I never be able to get in or out of diagnostic mode again? Have I created a fatal incompatability on my Kindle that will screw up other processes?

Is there a way of adding screensavers that doesn't involve entering diagnostic mode, or should I just forget it and leave well alone?