I have had poor luck with two multipurpose sensors correctly indicating open/closed (in the “use for a garage door” mode). They work fine for other purposes, but their vertical-axis measurements were just plain wrong.
I agree removing (and replacing) the battery in these sensors is nasty (and I don’t consider myself feeble 
). There is virtually no ‘give’ in the plastic tab that is supposed to spring back into place to hold the battery.
Did it happen without any other change in devices?
I have two, and both have been nothing but problems.
And I also have arthritis in my hands, and it’s agony to work with that battery.
This is a case of extremely poor engineering. I just won’t buy ST devices, not unless I know they actually get in some usability people.
Yes, no change in devices but I must have been messing with my router at the time. I started wondering why my front door lock was not auto-locking, it turns out ST didn’t know the front door was opening and closing.
It was also about the same time I started playing with a mood cube that I couldn’t get to work… well duh me, it wasn’t reporting acceleration that’s why 
You know, to add insult to injury, for the first time last night we forgot and left the garage door open.
Now, if only we had a sensor that could have triggered an app to text us that it was open…
I am having the exact same problem as you. Sensor in garage door mode, and at 77% battery and not reporting open close, or even that the door is in motion but it still reports temp. Nothing but the temperature since Oct 3.
This is the second time I have had problems with this sensor in using it to monitor the garage door. Then I called support and found out that when in garage door mode, it only uses the tilt to detect what state the door is in and will ignore the reed switch/magnet. I have not had any problems with other multisensor when using the reed switch/magnet setup.
For our peace of mind we got the Chamberlain MYQ installed on our door, before we even got the Smartthings hub. It has an auto close function to close the door after a period of time that you can set and it can email/text you when it is left open. They have versions for both branded (MyQ Internet Connectivity Kit) and generic(MyQ Garage) door openers. The app is not too bad either. The downside is that MyQ is no longer supporting Smartthings, which for us was disappointing, but not a show stopper.
I hope that you will post how well the Echolink sensor works for you, I might follow your lead.
Something we are considering.
I will post on how the Ecolink works.