Loop sounders showing removed

[Galeon]

Got a couple of jobs where suddenly for no reason , Apollo loop sounders showing removed.
Whilst the panel is in fault checking the analogue value , of the particular devices returns a value of 16 .
They are the wall mounted type , they are sitting on a single loop panel , about 40 devices , with about 12 sounders , software 4 zones so isolator in and out each zone.
Anyone had any similar stories with this kit lately.
Panels are Morley and a Global .

[Wiz]

Not had any similar problems recently from Apollo kit.

Obviously could always be a faulty batch but this, anyway, would only relate to newly installed devices.

The first thing to ascertain, if existing system, is if anything has changed with the system recently; new equipment added, operating or configuration software changed in panel, changes to wiring, earth faults on loops etc. etc.

If none of the above applies then electrical or RF interference may have started from something else and which is affecting the data on the loop(s). Any new electrical systems or processes been added recently at the site?

[Graeme]

i have had loop sounders go into comms fault for no reason during maintenances. Sometimes they can be rest by sending them a test signal but other times they had had to be replaced. It has also happens frequently with AFD in Aritech panels.