@ssdnvv Do you have your other APs connected through one of the LAN ports of your TO? I had problems with roaming, too. I was able to fix it by connecting my other APs through a switch connected to the WAN Port of my TO. I then switched the WAN Port and one of the LAN Ports (assigned eth2 to br-lan and Lan4 to Interface WAN in LuCi -> Network -> Interfaces, you then have to switch the ethernet-cables, too, of course).
This fixed all of my Roaming Problems I had with TOS 5.X.
There seems to be some problems with switch configuration in TOS5.X due to switch to dsa from swconfig. Some traffic seems to be unable to pass the switch, especially when you use VLANs on the LAN ports (interfaces LANX.X). I suspect some IGMP-traffic isn‘t handled correctly but I didn‘t debug this further because I‘m fine with my workaround.
EDIT: Using my workaround my network is rock-solid 