@domseb; you’re not alone. I have this same issue (see post here: [SOLVED but hopefully not the last word] Photons lose connection to wifi—any ideas?) and have no answer either.
I have 1 photon running tinker and not connected to anything else just to see if it fails WiFi at some point. It does fail but much less frequently than the photons I run my app on. I cannot definitively say it is the photon, my app, router or other environmental circumstances. Just to keep my stuff going, I just implemented a watchdog that resets the device if the comms are down - yeah, I know, shotgun approach, but at least i can continue development elsewhere in the hope to return to the WiFi disconnects later on.