@electrik Yes, I drilled a 6.5mm hole, just big enough for the SMA connector to fit through and then screwed the antenna back on. Because the plate sits inbetween the radio and antenna, and touches the outside of the SMA, it is connected to ground.

Finally fixed as detailed here https://forum.mysensors.org/topic/10138/repeater-node-causing-problems-solved/25

So after some considerable time and loss of sanity I now appear to have a stable setup. I'd like to share what I have done in the hope it may save others a lot of time and frustration.

By enabling debug in the sketches, I eventually realised that I could not get any node to communicate reliably with the gateway. I was getting lots of NACKS even at short distances.

I was sure that the problems were radio related but after trying many NRF24 modules I was about to give up.

Then I read a post somewhere about ground planes.

As a last resort I added a piece of aluminium between my gateway antenna and the radio. (PA/LNA Version). Eureka!! This has pretty much solved the NACK issues.

Following this one or two nodes still intermittently lost contact after a few hours or days. What is strange is that even if moved close to the gateway, errors continue until the gateway is power cycled? I still don't know why this is.

I solved this problem by converting the Node PCB antennas into a dipole antenna as detailed at https://www.instructables.com/id/Enhanced-NRF24L01/.
Now all nodes stay connected.
Now after a couple more weeks of testing all is still good.

I am using Domoticz with the MQTT output passed onto Node Red and now have some really cool things going on.

A big thanks to all that replied and pointed me in the right direction.

@sundberg84 Thanks. I will aim to get both sets of logs. What I am asking is if this can be done with Myscontroller alone, or if I need to connect up my FTDI?

I am using ethernet gateway and can connect to it with Myscontroller.
Can I view debug logs of the remote nodes using this method or do I need to carry on debugging each one with usb/serial converter?
To debug the gateway with MyScontroller I guess I need to enable dubug in the gateway sketch?
I do not use OTA updates. Still trying to get reliable communication between nodes and gateway without NACKS.

I think I have fixed the issue. I changed to the cap on the ethernet gateway from 47uF to 1uF. I have power cycled the gateway 4 times now and all the nodes came in. Looks like less is more! For whatever reason the breakout boards obviously don't work well for me.
I will keep testing for a few days.

@mfalkvidd No I only use one at any time.
I started with serial and then built the ethernet gateway. To eliminate the ethernet gateway hardware I just reverted back to serial to test.

@yveaux I have a serial gateway built on Arduino Uno connected to Pi. This is now just spare as I have W5100 / arduino nano ethernet gateway. Nodes are mostly 3.3V pro minis. One is 5V nano. All arduinos are clones.
Radios on nodes are NRF24L01+. On gateways I can use NRF24L01+ or amplified version (doesn't make a difference to this behaviour).

As an example I switched off the gateway 2 hours ago. 2 nodes are came in straight away, the other 3 have no communication. Chances are the same 2 will connect again if I power cycle the gateway but the nodes that work straight away changes randomly. It seems like the gateway does not want to acknowledge certain nodes.

Behaviour is the same if I revert to stock motion sketch.

The parser says that no radio ACK has been received when the node tries to ping the gateway.
I have today built a replacement radio breakout board from scratch. The problem is still the same.
Some nodes connect, some randomly do not.
I have replaced every piece of gateway hardware, so this my be something within the Mysensors code.
Any suggestions please?

@mfalkvidd Thanks for that.

F11 showed that the page was failing to resolve cdnjs.cloudflare.com
I run a pihole so just needed to add to my whitelist.

Fixed. Thanks.

Now back to the node/gateway communication problem!