Negative values in dashboard


not sure where to put this.
I've still an old flukso meter.
Recently I'm seeing negative values in the graphs.
For example today at 22:20 I had -41000 ...
At that time it will not be due to the PV installation ... and normally the wiring is so that it doesn't measure the the PV part.

Time to replace the meter/sensor, or some hiccup in the site displaying the info ?