I have an RPI 2b running Kali 2. WiFi adapter is a TP-Link TL-WN722N running in monitor mode while the RPI is Ethernet connected to my LAN

I'm not really using it to hack into WiFi, i'm just using it to detect MAC address and the RSSI signal strength. The RPI captures the data required via Tshark and sends the data to a MySQL server

This is my tshark command
/usr/bin/nohup /usr/bin/tshark -l -I -i wlan1 -T fields -e frame.time_epoch -e wlan.sa -e radiotap.dbm_antsignal -e wlan_mgt.ssid -E occurrence=f type mgt subtype probe-req | /usr/bin/php /opt/dronecapture/tsharkparser.php&
The problem i have is during really busy periods... when i am seeing large amounts of devices ( MAC addresses ) the RPI stops capturing traffic. The RPI seems fine, i can log into it, get onto the web run various commands and tshark is still working but i am not receiving any data.

The problem seems attributed to the TP Link but i'm not sure what / how to check. if i run a ifconfig the TL link is listed as Wlan3 i can also run the following
root@Drone:~# dmesg | grep -i wlan3
[    5.539336] ath9k_htc 1-1.3:1.0 wlan3: renamed from wlan0
[    5.608374] systemd-udevd[160]: renamed network interface wlan0 to wlan3
[   21.144337] device wlan3 entered promiscuous mode

[    2.273783] usb 1-1.3: Product: USB2.0 WLAN
[    2.275528] usb 1-1.3: Manufacturer: ATHEROS
[    2.277204] usb 1-1.3: SerialNumber: 12345
[    4.513412] usb 1-1.3: ath9k_htc: Firmware htc_9271.fw requested
[    4.515626] usbcore: registered new interface driver ath9k_htc
[    4.818512] usb 1-1.3: ath9k_htc: Transferred FW: htc_9271.fw, size: 50980
Everything seems fine but the TL link seems to have just stopped capturing.

Has anyone else had this issue? or can anyone suggest anything to try and find out what has stopped working.