Don't have the answer, but might be able to point you in the right direction.
I've got the 2467B Maint/Service manual in front of me. But as usual, it's not detailed
enough for me to pin-point your error code.
(Page 6-12 in manual, if you find one)
Test 5 is a test of the Main Board.
The errors listed are for Level/Trigger, but your #9 is not on the list.
Most of the errors like this I've seen, have to do with the trigger level.
Too positive/negative. (Usually just a pot adjustment)
Manual says to clear all this type of error code, press the A/B Trigger Push-Button,
which you already know.
Hopefully somebody else on this site will be able to pin-point the exact problem,
but this gets you in the ballpark.
Most of this type of error doesn't cause scope failure, it just alerts you to the fact
that an adjustment is just out of tolerance.
Good luck.