Firmware Version: RouterOS 7.1.
Router: HAp ac3 and HAp Lite.
Configuration: 2 Different Tx Chains are configured by enabling the check box.
Scenario Description:
During Association, the non-AP station sent HT Capabilities with the Tx STBC Bit cleared, then the AP Station replies with Tx STBC Bit Set with a status code success, (Then Capabilities Matched and accepted that STBC Is not supported).
During the connection throughput dropped to the half, after captures, it seems like the AP is sending frames with the STBC Feature, where a duplication of the frame is sent on two spacial streams.