I have a Suunto bike POD, which is - I believe - the same as the Wahoo combination sensor, and is a finnicky device. Here are my steps for troubleshooting its flakey performance and turning it into something useful:
- Spoke magnet: this will always come loose. I apply blue thread lock, tighten the screw, and then build Sugru around it to further support it.
- Spoke magnet/speed sensor: Suunto say the spoke magnet and speed sensor (a reed switch) must be within 4mm of each other. I disagree: 2mm seems to be safer.
- Sensor housing/frame attachment: I wrap the bike frame with electrical tape, partly to protect the frame, and partly to provide more grip. I then zip tie it very tightly in place, so that it can't move. Remember: 1mm of movement can equate to no speed data, which equates to no distance data, even with a GNSS connection.
- Cadence magnet: my bike frame (Canyon Grail CF) doesn't have enough space between the crank and the frame to use the supplied rubber housing. Instead, I 'built' my own housing out of more Sugru: the magnet is exposed to the world, but passes within a functioning distance of the cadence sensor (another reed switch). It hasn't fallen off, even after some very rough (washboard) gravel rides.
- Software troubleshooting: the sensor has red and green LEDs. Green indicates the cadence sensor is functioning, red is speed. This is helpful, until they stop activating (only a few times per sensor activation). Using the Wahoo app (not the ELEMNT app), you can navigate to sensors, pair to the speed sensor, and see data from it much more easily than using the watch: Immediate speed/cadence data as you move the magnets near the sensors. Invaluable.