@iam_yotka 

Hey

Its worth noting that OFDMA does nothing for aggrigate throughput, this is a method for increasing capacity on WiFi networks.   Its not unheard of to have reduced througput speed when OFDMA is enabled.  However I have not seen it usually being this drastic a drop

OFDMA could have the following negative effects if enabled in low congestion settings.

1. As you are allowing the airspace to be devided into subcarriers, each user will get less bandwidth overall

2. During the subcarrier creation, bandwidth will be allocated out to slower devices and therefore any faster device will have additional wait times or latency

3. There is no guarantee your device will be allocated the complete channel width per packet, therefore your throughput will be restricted.

4. Not all devices support this, non supporting devices will cause a mixed mode effect that must be compensated for by the AP ultimately increasing latency

This should only really be enabled if congestion is an issue, if speed is your concern disable this to ensure devices are not sub-carriered and therefore get the full channel width per packet sent.

This article below is a lot more detailed if you are interested..

https://www.smallnetbuilder.com/wireless/wireless-features/33223-does-ofdma-really-work-part-2?start=1

Its broadcom chipset issue - www.snbforums.com/threads/sta-to-sta-ofdma-issue.74943