I can appreciate you say you have exclusively used the mobile Perspective application, but have you tested it on a regular browser to prove that it isn't a mobile application specific problem?
Also, when you say you have configured the gateway for a 2 hour log out, are you in fact referring to the Perspective project inactivity and session timeouts? Maybe take a look at the project settings here:
You might also find this post interesting:
[FEATURE-13370] Perspective login timeout and auto-relogin - Ignition Early Access - Inductive Automation Forum