I have the Home Assistant Voice Preview unit and it wakes up too often at random intervals trying to answer questions it thinks it has heard. This is happening a lot when the TV is on.
I have the Mycroft wake work and it is set to “slightly sensitive”.
The most annoying thing is it wont stop when i tell it to stop and keeps listening to whatever the TV is saying and then trying to curate a response on what it hears.
It’s gotten a lot worse since the last firmware update. I am on 25.5.2
As you have realised, it wakes because it thinks it has heard the wakeword, and yes TV is so often the culprit. This is the main reason for choosing a longer and uncommon wakeword.
It stops listening when (what it thinks is) voice stops talking. Rather than telling Assist to stop listening, you need to stop the TV from talking. Yeah, i know that is impractical. Or have i missed something and Assist now starts processing the command before we finish speaking it ?
Voice Assistant has come such a long way in the past few years … but there is still plenty to improve … such as identifying who is speaking (you or the TV?). Humans can easily focus on one individual voice in a noisy or crowded room - but to a computer it’s just noise. Makes me realise just how much our ears/eyes/brain does that we just take for granted.
You might like to try some of the other combinations of wake word and settings.
I used to have the wake word “computer”. That put an end to watching Star Trek. 
Thanks for the reply. I am using the Home Assistant Voice Assistant and it only has 3 wake words and I cannot change it.
I saw it was reported as an issue with the previous firmware and it has since had an update. Hopefully, this will solve it. So far it hasn’t been triggering again.
The assistant is designed to wait for follow up orders, so it keeps listening and replying to what it hears on the TV. Usually, if i shout “stop” it will stop what it’s doing but it is ignoring me.
Hopefully, things have settled now since the update the other day.