Check either live or past logs or the "Events" tab on the device. Many people have had problem with the ST Button sending duplicate events, especially on older versions of the button firmware (only update-able if paired to ST) or if the button had been dormant for a while. Checking these will tell you if that is also happening to you. This thread describes a similar issue (and other possible problems in case it's not what I'm thinking).
This other thread has a bit more on the duplicate-press issue and a custom driver that may work around this particular problem if that is what you're experiencing and a firmware update doesn't work for you.
