Both my wife and I have experienced odd high HR readings that were bogus. What I do is take my pulse either at the wrist or in the neck. I use a 5 second time and multiply by 12. I used to do this when running and I did not have any HR monitor. If your HR is really 180, you will know when you take your pulse. That is going to be 3 beat per second. You can tell that easily without a timer.
I would assume it is a glitch but easily verifiable.