wireless link bridge-wds in one way slow

help to solve or understand little prob with wireless-link about 8 km,…

both sides with Lobometrics 968T ( mikrotik board x86 OS3.xx)

distance : 8km free line of sight both sides with parabolic antenna d=65cm 29db cable lengh 5 meters

side a: bridge mode / 5ghz turbo freq.5250 / tx default / nstreame, polling (excat size 4000)
TX-signal strengh: -66 / SNR: 26 / CCQ 95%

side b: station-wds / tx-signal strengh -65 / SNR 23 / CCQ 70%

If I do bandwidht-test in winbox , setting side “a” in server-mode and side “b” as client I got following
result: receive only 20-22 MB / send 60-70 MB,…

After change this ( side “b” server , side “a” client ) I got the same result in other way,…
result: send 60-70Mb / receive only 20 MB recieve

So the transfer rate from “a” to “b” is only a 1/3 than the other way from “b” to a"" ,…

Why ? I have no idea what there may be wrong or not correctly configured, …

Anyone know this this problem or could help me to solve and optimize the link ?

Thanks

Mikaha

Try to change freq. they usually help.