I have an MT RB2011 and RBD52G-5HacD2HnD-TC: hAP ac² Dual-Concurrent 2.4/5GHz AP

Port based vlans
bridge
vlan2 (ether2) 1Gbps
vlan3 (ether 3/4) 1Gbps

I have a ReadyNas media device connected on vlan3/ether3. on snet 192.168.5.3/24 bonded nics @ 1Gbps
I have a MT hAP device connected to vlan3/ether4 on MT RB2011 providing 5G wifi connections on snet 10.0.0.3/24. (all ports are bridged to same wlan2 on hAP)

When I Rx ISO files on the ReadyNas device through the MT hAP device from a WIRED winbox I get nominal 110 MB /sec
When I Rx the same ISO files on the ReadyNas device through the MT hAP device from a 5G WIFI connections I get a miserable 15-20 MB /sec (My 5G Rx connection is roughly 880Mbps)

Why?? Thought it would be much higher... Bad setup config?