Monitor traffic with Wireshark on a Raspberry Pi as Access Point

I have a Raspberry Pi working as a wireless access point for my own home network (not connected to the internet) running on my wlan0 interface. I have Wireshark running on my RP AP and i would like to use it to monitor all traffic going through it. If i use Wireshark to monitor the wlan0 interface i can see all traffic directed to the AP (e.g. DHCP requests). I cannot, however, see any of the packets being exchanged between the different clients connected to this AP. Note that i'm already in promiscuous mode.

Oddly enough (or not), as soon as i switch-off one of the clients connected to the AP i start seeing all the traffic directed to this client.

What am i missing? Is there any way to monitor the traffic that goes through the AP?

Thanks