An update;
I have run since my last post and just now detected a network subsystem hang.
With the debug code that I added I can see that the uip_process in the uip.c
file is receiving packets but always drops them. The main OpenSprinkler
code never gets the packets. There is clearly something wrong with packet
handling since even ping does not work and ping does not involve the OS code.
I have been communicating with jandrassy, one of the maintainers of the
UIPEthernet code. That thread is here:
https://github.com/UIPEthernet/UIPEthernet/issues/129
He has been chasing a memory leak in this code.
There is a memory heap manager for packet buffers called mempool.c.
He suspects that the problem may lay there. Since I am seeing receive
buffer overflow errors in the ENC28J60 chip the problems could be related.
I have added code to check for this and will start another run.
It took 2 months to catch this error it may take a while to catch another
error.