Odd readings showing in Grafana with Icinga2 and InfluxDB

Within Grafana I am seeing odd readings in my graph for the current readings the current bandwidth in use.

Every so often the readings drop to -x Gbps which can be seen below.

I am using the query -
SELECT 8 * Derivative(mean(“value”),1s) AS “value” FROM “FW Int In SNMP” WHERE “hostname” = ‘Leamington FW’ AND “metric” = ‘eth_in_bps’ AND $timeFilter GROUP BY time($interval) fill(none)

I am unable to find the cause of the sudden drops as nothing is happening on the network to cause this.

Has anyone else seen this before?

Unsure if this is the place to post this issue.

looks like counter resets. try non negative derivative

Thanks! That seems to have resolved the issue.