99 percent certain the problem is the system is hearing "stop" for whatever reason.

 

Run the voice training again.  And please keep your mic a bit further away from your mouth.

Does the system hear "stop" still at the same moment? Besides, it was really quiet...and I don't know why the system could hear "stop"

Does the system hear "stop" still at the same moment? Besides, it was really quiet...and I don't know why the system could hear "stop"

 

 

The shorter the word, the easier it is for the speech recognition to accidentally detect it.

 

You probably mumbled something or coughed, and the speech reco system somehow heard that as "stop".

 

I'll release an update and change "stop" to "reject reject".  That phrase would be much harder for the speech system to accidentally detect.