I’ve had a very tough time working with the Smartthings presence sensors. First, I tried adding my phone (see my previous post) which never picked up for more than 45 seconds. Second, I’ve tried adding the Smart Presence sensor that came with my kit. I couldn’t keep my keys in the car in the garage because it couldn’t see the Presence sensor. Even when I bring the keys in the house, the sensor is doing the “away”/“arrived” cycle every ~10 minutes that the phone was doing before I had issues with multiple devices.
I’m getting very frustrated with the presence sensors and hopefully can get the Tasker setup working eventually. I’m still struggling with how to set up the Rest API as a Switch Toggle so that I can use the http on Tasker.
I have 2 ST presence sensors myself, I find them pretty reliable. First the obvious question is have you contacted support and if so, what have they instructed you to do thus far to resolve the issue?
If not, what is the house built out of? What lies between the hub and the Garage? Have you made sure that your hub is away from your router (as far away as the cable connecting the two allows)
My SmartThings presence fob worked abysmally until I put a powered motion sensor in the garage. This is when the hub was in a room directly above the garage. Since doing that, mine has been as reliable as any other of my SmartThings.
Can’t help you with the phone based presence detection as I have no confidence in it (based on too many discussions here).
+1 on what @scottinpollock said. My presence sensors work great with the plugged in motion sensor in the garage. Only had problems one time and after a bit of investigation discovered that the motion sensor had gotten bumped and was unplugged.