Dave, did you solve this disconnect issue?
I find a similar disconnect of some devices when using the Ewelink integration in Home Assistant, whereas the Sonoff devices work fine when controlling them directly from Ewelink. So it's not a Wifi disconnect, but rather a HA <-> Ewelink disconnect, and it happens differently for different devices. I.e. one Ewelink device works in HA at some point, while another one does not, and sometimes both works in HA, and other times none work in HA.