I'm assuming the tx/rx values are collected as part of the sensors collection (at least on Cisco, TX/RX of SFP's are usually reported as sensors whose values can be read).
It might help if you set 'nav.ipdevpoll.plugins.statsensors = DEBUG' in `logging.conf`. This should debug log the raw values NAV reads from the device. There might be something wrong that happens when converting the number to the given precision of the sensor.
I'm assuming the tx/rx values are collected as part of the sensors collection (at least on Cisco, TX/RX of SFP's are usually reported as sensors whose values can be read).
It might help if you set 'nav.ipdevpoll. plugins. statsensors = DEBUG' in `logging.conf`. This should debug log the raw values NAV reads from the device. There might be something wrong that happens when converting the number to the given precision of the sensor.