You're looking at catastrophic failure of the system.... The fault supposedly relates to a bad nand or a bad flash however I cannot find consensus on the causes of this issue. Unfortunately the only solution I have seen that works is sending the system back to Sony for a paid repair if it's out of warranty.
I wonder, Did he attempt to flash with service mode active or did he use service mode at any point? Did you attempt to exit service mode once you had arrived on 3.41?
Things to potentially try (note these are all guessing suggestions and I take absolutely no responsibility for any further damage incurred):
1) You should attempt to exit the service mode on 3.41 based on the chances it still may be active.
2) Place a later firmware on a FAT32 formatted USB stick in the correct location and try a system update from recovery mode again.
Since he had a modified/patched firmware on there and you've also downgraded it, he has likely lost blu-ray support in the process which would require a separate fix anyway, Hopefully he had a backup of the correct directories before you attempted it.
I am afraid that Sony will likely know what you did if you send it back to them in this state.
Thrown in the towel - Deletion requested.