Gaps in Power Chart, but no bad data?

I've got an issue with the Power Chart that is confusing me. There are gaps in the lines, but I don't think there should be. This seems due to the "Show a break in the line when data is missing" checkbox, which I get is the same as the pens.display.breakLine property. I assume "missing" means bad quality data, but there isn't any, see below.

My colleague thinks this has to do with the fact that Historical Deadband is set to Analog, but I don't think so.

For example. Power Chart with gaps at the top, regular Time Series Chart at the bottom.

There are no bad quality points in this time frame:

This is on 8.3.7.