Fault – Please can you help diagnose the cause!

Situation:
I have 2 handsets Account #1= 095344440 and Account #2. 5344440-1
Both are registered and work fine when the status line displays e.g.: L1: 095344440
Or L2: 095344440-1 see photo 3

Problem: Sometimes when I try to dial out I notice the status line shows L6 IP Call
See photo 1
and I get “Called failed” in the status line
and error in red Via IP Call, the number I was dialing and “New Cable”

Please can you help me fix this issue?
I can seemingly work around the issue if I turn the handset off for a minute and reboot it. The other one will be working just fine while I have an error with one. What’s going on?

Many thanks
Ian

  Yealink Fault.docx (Size: 498.58 KB / Downloads: 1)

  photo 3.JPG (Size: 118.58 KB / Downloads: 4)

  photo 1.JPG (Size: 104.13 KB / Downloads: 4)

  photo 2.JPG (Size: 102.45 KB / Downloads: 4)