@John K: I’ve updated the firmware — it’s at the same folder, and I added today’s time stamp so we know this is the most recent version:
http://raysfiles.com/os_compiled_firmware/v3.0/experimental/
The Ethernet library’s write function is technically incomplete: it’s supposed to be able to send a buffer of any size, but apparently it only sends the first 2048 bytes of it, resulting in incomplete Json data. I’ve raised this issue in their Github library:
https://github.com/arduino-libraries/Ethernet/issues/141
and I’ve fixed it by adding a loop until the entire buffer has been sent out. I’ve tested the new firmware with 20 programs and it works fine so far.
@bena: given your description, the controller is at least not freezing, it just stops responding to web request. There are several possibilities, one is if you have a relatively large number of zones and/or programs, maybe the issue you encountered is the same as what John K reported. An easy way to tell is to export your configurations to a file and open it to check how many characters it has. If it’s larger than 2048, it’s very likely the same issue, and just flash the Jul18 version of the w5500 firmware. That should fix it.