catbus The forum is more “Front End” heavy than traditional ones like EB (Powered By PHPBB)
To try to explain this in simple terms. The web browser is doing a lot more work on this forum and the server is doing less work. Some phones, depending on the type of phone or type of browser in use might have issues.
That said, I doubled the capacity of the web server today and in monitoring, resource use is down to half, as expected.
Debugging mobile devices is quite difficult also as they may be on 4G, have a weak Wifi signal etc.
To rule out a few potential issues you may want to simply restart your phone and see if this helps.