Whole network stops transmitting.

[Felix]

The radio RST is active high, unlike the MCU resets which are active low. Maybe unfortunate because otherwise it could be coupled to a watchdog timer like Neko's TPL5010.
In addition, it requires a HI-Z on the RST pin while powering up the radio. A reset requires 100ms HIGH on RST then wait for 5ms before initializing the radio.
See section 7.2 in the datasheet.

[vooyeQ]

Having similar issues, running just 4x Moteino R6 433MHz units.

Gateway powered by a Raspberry Pi via USB connected FTDI, 3 battery powered nodes (18650, 2 nodes outside, one inside).

Outside nodes seem to die due to a sudden raise of temperature, recently 0.0C to 18.0C in a few minutes, but it happened a few times already with lesser temp deviation.

Tried:
1. gateway intact, all nodes powered off, arbitrary node powered on
2. gateway powered off, nodes left intact
3. gateway powered off, outside nodes powered off
4. gateway powered off, outside nodes left intact, inside node powered off

Have to power off all of the units and power on again, works like a charm then.

Battery voltage > 3.5V.

[Felix]

I would try to eliminate as many variables as possible which could lock up the nodes in any way.
Just a suggestion: power nodes with a more comfortable head room, say 4v if you expect significant temperature swings.
I would make sure you use antennas properly, depending on the type.
Then of course... how you use the library code is crucial. The library does not come with any guarantees that the user code will not fail.

[vooyeQ]

Reassembled all the nodes, updated with the newest libraries (gateway was up to date last time), FTDI adapter changed.

Antennas are simple helical ones, perpendicular to boards.

Small steps.. time will tell, waiting for next temperature spikes.

Ordered 3 more units to experiment with different sketches and register setups.