Yeah those 2 lines have been an issue for quite sometime, unless you are running a Pi3. But I believe on the latest image @TrystanLea has now moved back to using the default setup (allowing the Pi to set these) which caters equally for all Pi’s.
What I believe is happening (and this is true and tested on the pre-emonscript images so may have carried over) is that your wpa_supplicant file in the boot directory is overwriting the OEM’s (modified permissions) file at start up as it is designed to in the OS image, then the OEM stuff (emoncms?) isn’t able to read/write as needed.
This has been addressed in previous images by loading the image to a sdcard then putting it in a Pi with Ethernet so that you can modify the location and symlink the OEM copy and then you can modify the wpa_supplicant file at will on a PC or via ssh or indeed still use the emoncms setup.
See Wifi config on Pi Zero using emonSD - #4 by pb66 although the rpi-rw is no longer needed and I think the source location of the OEM file has maybe changed to.
Brian or Trystan may be able to advise more on the current image, I have to say I thought this was going to be implemented on the emonScripts images TO enable the use of Pi Zero’s without any additional difficulties. Perhaps that was missed or not working quite right? What files do you have in the boot folder?
ls -la /boot
anything there wifi related that isn’t the wpa_supplicant file?