I still have my yellow by one, slightly modified jack end
Like this is what I use
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F254245653828
Wireless ones better yeah? Like Honeywell hkc , do texe do a wireless smoke?
I mean wireless with built in sounder of course so can act independently , not that it can take the place of a proper fire alarm
Long shot does this have a back tamper switch fitted ,maybe someone modified it or something and it isn't making contact
I don't understand how your exiting engineer mode , so maybe there's an extra switch h somewhere programmed on to a zone or something
Don't worry an expert will turn up soon lol