Why are my sounds profiles automatically changing on my HTC One M9?

[AC Question]

Sounds Profiles automatically change on HTC one M9

I set my phone to vibrate, however after taking a call, the sound profile automatically resets to normal, meaning with receiving an incoming call or notification afterwards it rings. This is incredibly annoying as I have to remember to switch back to vibrate profile after every call. Is there a way to stop it automatically switching back?

Regards