Thought I would update this thread, still struggling but made some progress.
I added the watchdog which helped somewhat, so far I have found a few things which I have fixed or investigated further on my efforts to make things more reliable.
My gateway crashes after a few days - unsure why, suspect its a power issue so I have ordered a standalone 5v to 3.3v power supply to run the radio. My setup is a Wemos D1 mini. I am wary of changing too many things at once but I am considering wiring directly to a PI for a gateway.
My side gate sensor used to drop off and come back after an hour or two. I noticed the TX was hovering around 90-100% so I thought it could be signal related, I built a mains powered repeater with the RFM69HW and placed it nearby. The side gate sensor favours the direct connection to the gateway but it seems to be more reliable. This sensor is a 1mhz/direct off the battery sensor.
My BME280 sensor crashes a lot, I think this is related to the temp sensor rather than the node, seems to stop returning measurements except the battery voltage for a few hours then stops entirely. This is a sensor with a boost converter and when it crashes it never comes back, has to be reset. I am going try a different library for reading the BME280 when I get chance. I have also observed it gets less reliable as the battery voltage drops below 2.5v.
Next up with annoying failures is my front gate sensor, previously most reliable it stopped working for 12hrs before magically reconnecting today, no reset required. It was rock solid till the battery voltage dropped to 2.5v, it's working now but I am going leave it to see if as the voltage drops the sensor becomes more unreliable. This sensor has plenty of signal strength to spare so I don't think the relay will help, its probably only 8m from the gateway.
The boost converters I am using are the cheapest ones commonly available from china. To continue the experiment I have ordered some slightly more expensive ones to see if the performance changes.
I do have the capacitors in place, but am wondering if its worth experimenting with the values.
People mentioned soldering/connectivity issues. I don't think thats my issue here. All my sensors are EasyPCB Rev9. Most of my sensors have no wires (ie no sensors, they're just testing their existence) or simple stuff like contact sensor or relay control
This is the relay I made, its got a custom PCB under the sensor with a HLK-PM03, fuse, thermal fuse and a few other bits. Debmowsk designed the circuit originally I just rejigged it so it can be stacked on top of the easypcb rev9
Far right of the graph shows the period the front gate sensor was offline for.