Issues with non_negative_derivative


I’m trying to grapha Tx/Rx stream coming from some SNMP monitoring.
The values are in Bytes and I understand I need to use a non-negative-derivative with a 1s period to obtain the Up/Down speeds.

This seems to work perfectly in InfluxDB with the following query returning the following graph:

SELECT NON_NEGATIVE_DERIVATIVE(mean("ifOutOctets"),1s) AS "mean_ifOutOctets", NON_NEGATIVE_DERIVATIVE(mean("ifInOctets"),1s) AS "mean_ifInOctets" FROM "telegraf"."autogen"."ifTable" WHERE time > :dashboardTime: AND time < :upperDashboardTime: AND "ifDescr"='eth0' GROUP BY time(:interval:), "ifDescr" FILL(null)

Now, in Grafana, connected to the same data, I get a strange graph that is missing values as below:

SELECT non_negative_derivative(last("ifInOctets"), 1s) AS "Rx", non_negative_derivative(last("ifOutOctets"), 1s) AS "Tx" FROM "autogen"."ifTable" WHERE ("agent_host" =~ /^$nas_host$/ AND "ifDescr" =~ /^$nas_interface$/) AND $timeFilter GROUP BY time($__interval), "ifDescr" fill(null)

Would anyone know what could cause such difference? What could I do to my qyery or graph so the data shows up properly?