It's possible to have the Audio Meter widget stop responding if you set the Gain really high. It will cease to work as long as the MetaSound window is open. Closing and reopening the MetaSound window will fix the issue.
See video for ref (this video intentionally has no audio for the health and safety of your ears) [Link Removed]
1) Launch any project with the Metasound plugin enabled
2) Create a MetaSound Source
3) Add a Sine Generator and an Audio x Float node
4) Add a Float Input on the Audio x Float Node
5) Connect the nodes to the Out Mono node
6) TURN YOUR SOUND OFF OR YOUR VOLUME VERY LOW DOWN
7) (I'm serious, this is going to get loud)
8) Play the MetaSound
9) As the MetaSound is playing, increase the Float input value to a very high number
10) Observe the Audio Meter
Expected Result:
The audio meter always works
Actual Result:
After hitting a certain value, the audio meter stops responding, even if the Gain is set back to a reasonable number
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-153359 in the post.