My 3400s EF, which along with the EE has performed flawlessly for almost 5 years, suddenly refused to shut down. Instead, it displayed a set of 5-6 character (text) lines including:
"INFO: RCU not detected CPU 0 stall (t=xxxxxxx jiffies)" -- where the 7 "x's" slowly rolled over, through various number values.
The only possible precipitating event I can think of was a relatively firm landIng (stuff happens) though after that it continued to perform fine through a long taxi until the attempted shutdown on the ramp, when it would not turn itself OFF. In efforts to try to get it to shut down, I switched both primary and backup power sources ON and OFF, with and without the EE, etc., attempted manual shutdown holding button 2, then 3, per the manual, p. 11 -- all without success. The unit remained stuck ON through another panel power up and twenty minute flight home. After panel shutdown there, it remained ON, obviously running on the internal backup battery alone, which held it up for 83 min. (Yay!) before reaching full discharge when the unit did, finally, shut down.
After being down for several minutes, I fired up the panel again, and got error messages as shown in the attached photo. The second to last line in the screen shot is cut off but reads "...unknown-block (0,0)".
It continued to automatically loop through multiple reboot attempts, without success. It has the latest Vs8.08.29-MV16 system software, which I have not yet attempted to reload.
Is this likely due to failure of an onboard system clock button battery, or something else? Can I fix it or do further troubleshooting without sending it in for further analysis & repair? TIA.