My phone a Moto E2 , 4G lte drops calls consistently after 15 minutes ans 20 seconds of conversation. Calls are on Wi-Fi. My wife’s phone is doing same ( same model). Why is this happening? Is there some method of turning off this time limit?
Sounds like a classic router issue. Basically the router it’s erroneously closing the path the audio is taking prematurely. It is basically a timer being run on the router, that is why it is so consistent. This is typically a bad ALG feature on the router.
Things to try;
Upgrade your router’s firmware. Might be a bug that has already been fixed.
Turn off the ALG functionality on the Router.
Try those things and let us know if it helps.
If you have a problem finding the ALG that @seanr mentioned it is usually called SIP ALG or NAT ALG and some ways to disable are here How to Disable SIP ALG on Popular Routers or post your router Make/model for additional help from someone