Domoticz

After a while (I have not yet been able to determine whether there is a specific time or interval) my Domoticz starts reporting:
Error: RFLink: Nothing received for more then 30 seconds, restarting...

It then tries to reconnect, and reports doing so successfully.
30 seconds later, I get the error again...

This keeps happening until I go in to the Hardware settings tab and disable (update) and enable (update) the RFlink hardware, after which it works again for a while!

IMO this means it is some software issue in the RFlink module of Domoticz, and not the RFlink itself.
(BTW: The RFlink is ping-able the entire time this happens, and the only change I need to make to make it work again is the action of disabling and re-enabling the RFlink in the hardware settings!)

Any suggestions where to start troubleshooting?

You mention ESP, is the ESP used as a wifi module for RFlink?
When used in the normal way, RFLink(Arduino Mega) to Domoticz there is no such issue.
This means that Both RFLink and Domoticz are fine. You need to check your ESP wifi code.

I am using the ESP as Wifi module (Using the board purchased from Nodo-shop), and when Domoticz is struggling, I can still telnet in and do manual PINGs and get the PONGs back, which is why I am suspecting there is something in the Domoticz module that gets confused and not the RFlink nor ESP8266, esp. as all it takes is a restart of the Domoticz RFlink software module (ie, nothing happens with the RFlink, it keeps running, it is just the software module that gets restarted) for it to work again!

It *looks* like this starts happening when the RFlink has been unreachable for a while (don't know exactly how long), as I had to restart one of my APs (the one the RFlink is connected to) and it started happening again... And turning the Domoticz module off and on again fixed it...