Wifi issues been trying to troubleshoot

Hi all,

sorry for my ENGLISH, but please try to understand.

i facing this problem like 2 years more or less i cant remember but i trying to fix this problem really seriously.

hardware never change is still say original.

ok here the problem i trying to seek for help.

whenever my iphone 5 turn on wifi if i keep using it my home network are fine.

once i put aside it will like few minute the disaster appear.

i remember before version 8 is the worst. it can lag until my modem disconnected.

1st i thought my modem are spoil but that time i already found out is this iphone cost this problem.

but i still cant believe it until i change new modem and it still the same problem.

so my wife just brought a new iphone 6s+ so finally the problem solve when i put this phone aside.

and i had this phone with me. i reformat restore everything to latest 9.2.1 firmware full clean restore.

had a normal chat apps install seems everything are fine. once like maybe few days later. the problem came.

once i turn on the wifi i checn with my windows PING IP and respond from 10 ms shoot up to 200ms.

and the phone now is fully stock and default setting.

nothing to upload but still same problem.

may i know who can tell this problem? for me no sign of hardware failure. because everything just working fine.

just this wifi issues yet the signal are working fine as well.

if regards the setting and all i already did look for google and turn off in every possible way.

so the iphone 6s + my wife using now is same setting from iphone5 that transfter over.

but no such problem appear.

or maybe there anyway can fully wipe clean whole internal deep inside memory?

i affraid there some virus or something stuck in it or something. just widely guessing.

thanks for reading and sorry for my english again.

wil try to correct my explain which some of you that would like to help yet cant understand.