Nothing to make them more stable per se (over rFM). I have 3 emonTX’s in close proximity to each other, one per phase next to where the power comes into the property in a workshop attached to the side of the garage. The other side of the single skin brick wall of the garage, maybe 10 feet away is where the pi is located.
On my data collection I would see random periods where one of the emonTX unit’s data feeds are all dropped collectively, suggesting that this particular unit cannot communicate. This was also verified in the emonCMS tool looking at the inputs screen and seeing the delays on the input updates in many minutes rather than within 10 seconds as they are usually.
Resolution was to move them all to USB serial and put the Pi in the workshop with them once I’d run an ethernet cable to that location.