APC have to strong signal for AP ?

Hi.

I hack power output on SmartBridges to 100mW (normaly about 54mW).

I set one AP in AP mode and other in APClient.
On both i set 100mW power.

They both "see" very goot each other. But transmission doesn't work.

When I change power on APC to about 70mW then it work.

It can be realy that APC have to much power for AP ?
Distance is about 1,5km.

Is this normal ?

Thanks for help
Pawelr