Details about the EAP225-Outdoor can be found in the other topic: Anyone working on TP-Link EAP225?
The flashing procedure is what @pdecat quoted, and is the same as on EAP245v3, EAP225v3, and EAP225-Wall. See the respective commit messages for more info.
I haven't heard about anyone having issues the 2.4GHz radio; this is the same on all the EAP-devices. Maybe you could post a dmesg output (or logread) in the other thread if there's any warnings.