HP 8753A S21 Noise from 300 KHZ to 1.1 GHZ

[outlawpsd]

I was playing around with my 8753A which also has the 85046A test set and went to measure the transmission loss for a cable.  I switched it to S21 and noticed that from 300 KHZ to around 1.1 or 1.2 GHZ the Log Mag plot was very noise, but pretty much flat after 1.1 GHZ.  This is a new problem that just showed up and I ran some self test.  Test 17 ADC Linearity failed.  I have not torn into it yet but wonder if the teo problems are related?  Just dont want to go down the wrong rabbit hole.  If anyone has any suggestions on where to start please let me know.  As far as I can tell  S 11 measurements are fine and so are SWR.

[outlawpsd]

Ran the Receiver Noise Level test from the onsite service manual.  A came out fine at 15uU but B came in at 502uU @ 3kHz.  I reran it at 10Hz per the manual and A again came out fine.  B was at 500uU for 1/3 of the test and then dropped down to 15uU for the last 2/3's.  Im guessing someone put too much power into it and it's now deaf in the lower range?  Any idea's where to focus in on?