So garage has no detector?
Maybe sensor playing up, when did you have system service last?
Requires some investigation really , seems your circuit is split , but if it's a tamper fault of some kind , while set can show as alarm from what I rember on those
Lock Smith's carry a tool slides over cylinder end tilt up and down fees seconds your done
I didn't have patience to watch video lol if that's what he did
Police say don't lock internal doors as they cause allot of damage
Personally nice loud internal bell , no open plan layout and lock them doors to slow them down , hopefully they just raid the fridge
Chimney breast no big deal , you don't have perimeter protection so intruder would access room either way and trigger it once in
I would move it first personally