I have a customer who uses Cisco SPA502G phones, from 5 months ago in October 2023, they have been complaining that their phones have been rebooting themselves from time to time.
The Reboot History under Info page shows that the Reboot Reason was System 4, picture attached.
This customer has been a loyal customer with us for 10 years, and therefore has been using these Cisco SPA502Gs for years, they moved their office back in November 2022. And the issue was firstly reported to us in October 2023. I don't recall the issue happening before their office move?
I worked with their IT guy who manages their Fortinet router, even with a Cisco SPA502G plugged directly into a spare LAN port in the Fortinet router (without being connected to the switch like other phones do), the particular phone still keeps rebooting with System 4 error.
I found a previous discussion with System 4 error,
SPA Reboot Reason "System 4" - Cisco Community
Thus I upgraded their phone firmware to the latest 7.6.2R version, but same problem was still happening.
Our client also tried bringing the phone back to her home network, and the phone did not reboot there.
Myself is using a Cisco SPA509G, I upgraded it from 7.4.9 to 7.5.2b and then to 7.6.2R, everything was good after the upgrade, no issue at all.
So now I personally think it is something special in our client's office network which triggers the phones' auto-reboot with System 4 error, but what is it? I have no idea. Does anyone have any experience or idea please?
