Basically this thread: 

https://community.tp-link.com/en/business/forum/topic/647180

Has this been resolved yet? How do I fix it?

I had fast roaming working, everything was happy. I then introduced Vlans 10,20,30, 40 etc

Client [iPhone] is on Vlan 30, and can ping all devices on all vlans. Client then transfers from 5ghz-> 2.4ghz band and is only able to ping items on the native vlan. No filtering or ACLs applied (fully open 'default'). Not sure why client can ping native vlan 1, but can not ping it's own vlan 30.... after transfer from 5ghz -> 2.4ghz

Turn wifi off/on to re-connect and client can ping all vlans as expected.