Hostapd + 4.19.40 + Edimax EW-7811Un fails to accept client connections

Start with the reproduction steps, the hostapd debug output, and the linked moOde Support Forum thread. Compare the 4.19.40 and 4.14.98 behavior with the Edimax EW-7811Un on a Pi-2B. Done means clients can connect to the Moode access point using the correct password without hanging the network interfaces.

Describe the bug
Kernel 4.19.40 + Pi-2B + Edimax EW-7811Un adapter results in hostapd failing to accept client connections. The error message on the client is "Incorrect password". Reverting to 4.14.98 kernel and no issues.

To reproduce

1. Download and install moOde 5.2 image onto SDCard
   https://github.com/moode-player/moode/releases/download/r52prod-fix/moode-r52.zip
2. Boot up a Pi-2B with Edimax EW-7811Un adapter and Ethernet cable plugged in
3. SSH pi@moode (pwd = moodeaudio)
4. Activate hostapd mode manually and then optionally restart hostapd in debug mode

sudo sed -i "/AP mode/,/$p/ d" /etc/dhcpcd.conf
sudo sed -i "$ a#AP mode\ninterface wlan0\nstatic ip_address=172.24.1.1/24\nnohook wpa_supplicant" /etc/dhcpcd.conf
sudo systemctl daemon-reload
sudo systemctl restart dhcpcd
sudo systemctl start hostapd
sudo systemctl start dnsmasq

5. Verify a few things

a. ifconfig (verify that 172.24.1.1 address assigned to wlan0)
b. On a client device for example an iPhone verify that SSID Moode appears in the list of available WiFi networks

6. Optionally restart hostapd in debug logging mode

sudo systemctl stop hostapd
sudo hostapd -d /etc/hostapd/hostapd.conf

Expected behaviour
iPhone client is able to successfully connect to AP SSID = Moode using password = moodeaudio. Sometimes 2 attempts are required.

Actual behaviour
iPhone client receives error message "Incorrect password". Any number of repeated attempts to connect to AP SSID using the correct password result in the same error message. This also appears to hang the network interfaces and the Pi must be power-down rebooted.

System

• Which model of Raspberry Pi? e.g. Pi3B+, PiZeroW
  Pi-2B
• Which OS and version (cat /etc/rpi-issue)?
  Raspbian Stretch Lite
  pi@rp6:~ $ cat /etc/rpi-issue
  Raspberry Pi reference 2018-11-13
  Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 7e0c786c641ba15990b5662f092c106beed40c9f, stage2
• Which firmware version (vcgencmd version)?
  pi@rp6:~ $ vcgencmd version
  Mar 27 2019 15:45:53
  Copyright (c) 2012 Broadcom
  version 2e98b31d18547962e564bdf88e57b3df7085c29b (clean) (release) (start)
• Which kernel version (uname -a)?
  pi@rp6:~ $ uname -a
  Linux rp6 4.19.40-v7+ #1217 SMP Tue May 7 17:22:08 BST 2019 armv7l GNU/Linux
  Logs
  Logs and additional information on the issue are in moOde Support Forum thread
  http://moodeaudio.org/forum/showthread.php?tid=1399&pid=10581#pid10581