no it wouldn't (bellbox) on a walk test. But I do think it isn't a panel issue
run a temp new cable to the 2 devices bet it doesn't continue
I think its external
It has to be wiring if it was panel we would get loads of returns which we don't the optima has a very low return rate and then its usually because its been wired wrong and blown
how do you report fault (ie tel line digi etc) to the fire panel? Is the intruder alarm compliant to bs5839, whats the standby time of the alarm (as the dialler will be powered from it if wiring direct) etc etc etc