My FR255 is on firmware 14.20. But, I think this bug is non-deterministic so can't say for sure it only appears in this version.
I had an alarm clock go off while running an activity. I have it set for vibrate and tone for alarms. The screen changed as expected to show the alarm time and the dismiss function for the START/RUN button. I pressed it, so the alarm screen dismissed back to the activity screen and the tone stopped. But, the vibrate ran continuously (not the periodic pulsing pattern), like the software had toggled it on and forgot about it.
I pressed more buttons, pausing and resuming the activity, and the vibration finally stopped.