iPhone 5 and above dont keep connect with wifi in ideal stage

Dears,
Did anyone face issue with iPhone devices (specially IPhone 5 and above), its disconnect from wifi after few seconds of idle stage then it will connect back auto after login iphone. I have hotspot setup in MT and its connected different wife’s in Hotel, all other mobile like android windows are working without any problem. I made enquiry in different location but no one identify the issue someone said it should be related with Phones but I am sure it is not only the phone issue because when I do some changes in DHCP server like authoritative=no and always broadcast=yes then I can see the change it is working. But I don’t know what is the actual problem, please advice.

Regards
Manoj Mohanan
Skype: manoj.m.dev

What Wifi AP from Mikrotik are you using ?

What does wifi debug logs show ?