SHM security keeps scrolling through Armed and Disarmed by itself. I tried restarting the hub but it was still happening. The alarm will always go off in this state. Yesterday it stopped setting off the alarm after one round. Today it kept going off and I had to disconnect the hub.
Here is a video of the behavior of the app:
Check your automations. Maybe you made a loop by accident…
Are you using virtual switches to automate STHM? If so change your virtual switch DTHs to ‘Simulated Switch’ instead.
Known issue and there are two different things that can cause it: preconditions having been deleted from your automations, which happened to some people, or changes to the “virtual switch“ DTH, so that you should use the “simulated switch“ DTH instead.
Both of these changes were undocumented and happened at about the same time, which is really annoying. 
See the following thread:
it did it to me when i got home from work today!!! when i pulled out my phone to figure out what was going on it stopped. my sonos alerts me to status changes with SHM.
Thanks @nathancu and @JDRoberts . I changed the virtual switches I had set up for Actiontiles STHM integration to simulated switches and it started working fine.
Although shortly after I armed the alarm after the fix, I had 3 motion sensors falsely indicate motion for the first time ever. But that’s probably a new and separate issue…