Interface bandwidth (in/out) colected from ZABBIX do not show network cut on GRAFANA

[joua06]

ZABBIX version 5.0.4
GRAFANA version 7.3.7

I'm polling network interface in/out traffic bandwidth every minutes from ZABBIX and would like to show those information on GRAFANA dashboard.

It works as expected until a network cut occured. ANy network cut is correctly seen in ZABBIX but not showing in GRAFANA.
GRAFANA dashboard setting are already set "null value" but this do not fix my issue.

I changed time series interval to 1 minute in GRAFANA in order to have same configuration as defined in ZABBIX but this didn't fix my issue.

I guess your support will be much appreciated