Whenever the tap0 or tun0 device came up, my wireless connection would go down within a couple seconds. This was frustrating.
I found that there is a file /etc/default/ifplugd that needs to be edited.
Make it look like this:
INTERFACES="auto"
HOTPLUG_INTERFACES="eth0 wlan0"
This will prevent the default up script from tearing down your wireless connection. By default raspbian has “all” in the HOTPLUG_INTERFACES, which is NOT what we want if using openvpn and wireless.