Extension Keeps Going Offline

I have my newest extension that keeps going offline. I set it up the same as previous ones, but this one is going offline it seems each night. If I go into the phone IP and update the “secret” into the phone SIP Authentication password. Once I do that and reboot the phone it comes back online and can receive phone calls, but then next day it is offline again. All the phones are Polycom VVX310. What should I be checking/changing??

I’d suggest changing the phone itself, as it sound like a hardware fault.

@david55 I swapped phones this morning with another functioning extension, and after about 10min it went right back offline. I’m going to delete the extension in PBX and recreate - is there a way to copy an existing extension so I can be 100% sure it is all exactly the same?

@david55 - So I took a phone off one of my rarely used extensions and swapped it for this one that keeps dropping offline, and now they both are doing. I didn’t change anything in PBX - I just updated in the phone the display names and the PBX secret to register the phones - any idea what else I can try?