Forge issues subdomains on mobile networks

I have a really strange problem.

I have a domain nwo.digital that I have pointed to Digital Ocean nameservers so that Digital Ocean can do all the DNS stuff. I setup a subdomain using Digital Ocean DNS service, so in this case qcnfibre.nwo.digital. I then setup a new site on my Forge provisioned server with the same domain. If I visit the site via wifi on my desktop and phone it works perfectly. However if I visit the site on my phone with wifi turned off it works fine initially, but I leave my phone idle for 5 minutes or so and revisit the site and it says the server can't be found, the DNS falls over and ping test bring back unknown host. At this point I'm not sure if it is a Laravel Forge issue or a Digital Ocean DNS issue and at a real loss as to what is going on. Has anyone out there had this same problem, I'm really lost??

p.s. The phone without wifi is connecting fine to all other sites, the domain dns changes have fully propagated.