I would assume it's more or less common case. Sometimes we can observe gaps in time series data in Prometheus.

After investigation, we found:

1. Prometheus was up all time and information from other exporters were exist.
2. According to "up" metric , exporter was unreachable.
3. Exporter pod was alive
4. Looks like exporter application by itself was alive as well, due to some messages in syslog.

Hence, i can conclude we have network problem, which i have no idea how to debug in k8, either Prometheus ignores one exporter (usually the same one) time to time.

Thanks for any hints