possible bug with netflow / insight reporting of bandwidth - opnsense gui

[jata]

I'm trying to get netflow / insight reporting working and having an issue with data in the opnsense gui when viewing interface totals / bandwidth.

For testing I stream a UHD film and I can see the the correct/expected data in reporting / health (I think this data is not from netflow). It shows data rate of around 20Mb/s and this is what I expect from a this UHD stream.

I then use reporting / insight for interface totals and looks ok for a while then drops to zero while the film is still playing normally and reporting / health also looks normal.

I'm not sure if I am stupid or if this is a problem with my setup or a bug.

See screenshots attached.

How can I investigate further?