I am facing the same issue with my hotspot.
I have a 750GR3 as hotspot router and multiple access points (some cisco, and Tplink). Also I have the same SSID for all AP. I have seen this issue in Iphone only but this is not happening in android. Below is the hotspot setting for my networks.
/ip hotspot profile
set [ find default=yes ] html-directory=flash/hotspot
add hotspot-address=10.5.50.1 html-directory=flash/hotspot login-by=cookie,http-chap,http-pap name=hsprof1 radius-interim-update=4m use-radius=yes
add disabled=no interface=bridge1 name=hotspot1 profile=hsprof1
/ip hotspot user profile
set [ find default=yes ] idle-timeout=1d keepalive-timeout=1d1h shared-users=3
/ip hotspot user
add name=admin password=xxx
/ip hotspot walled-garden
add comment="place hotspot rules here" disabled=yes