Ring Alarm not activating immediately in Home mode

Setup:Home mode = upstairs disarmed and downstairs fully armed (used for when we sleep at night).So upstairs IR sensors are inactive but the downstairs ones plus door/window contacts are all armed.I have a 30s entry/exit delay in this mode.My front door is "main" but EVERY other DC is "secondary".My Garage is "entryway" but EVERY other IR is "room"This means that apart from upstairs sensors and downstairs front door/downstairs garage, EVERY other downstairs sensor should trigger the alarm immediately.However, I've found that when in Home mode, I come downstairs (and I've forgotten to disarm) but when I get sensed by the hallway IR sensor, the ring base station light turns red but nothing happens.Approximately 7-8s later, THAT's when the alarm sounds.Now the way I've set the system up, the alarm should be sounding IMMEDIATELY from when the hallway IR sensor picks me up as it's classed as being in a "room"....so why the 7-8s delay?Does this mean if we get burgled during the night, the burglar has 7-8s of "free rein" to march through the hallway and smash the base station to bits to disable the alarm system?Why is it not sounding immediately as it is meant to do?