Excellent. Thank you for clarifying.

It's just with this type of problem, we need the most precise information.

Please reconfirm our understanding of exactly what's occuring >>> During the times that the "single-ring" problem is occuring on the 3 back office phones: During an incoming call, the customer receives only a "single-ring", however the line button continues flashing. Once the flashing button is pressed, the incoming call cannot be answered.

Is this precisely what's happening?