Brief SoftAP Connection Loss During WiFi Connection Attempt

### Basic Info

Hardware: ESP-12S

### Description

When the SoftAP is active (the ESP8266 is acting as an Access Point), I attempt to connect to a WiFi router as a Station using WifiMulti.appAP("SSID", "PASS") then WifiMulti.run(). On successful connection, I notice that the SoftAP signal that is being broadcast is dropping out momentarily.

It's pretty hard to capture but I've been testing from my MacBook Air with https://packetsender.com/.

### Order of Events:
1. I set WiFi.mode(WIFI_AP_STA).
2. I fire up the SoftAP and start a UDP server with a hardcoded IP address and port.
3. I then wait for a message from PacketSender with the SSID and Pw for the WiFi router.
4. I take those credentials and attempt the connection, this is where the SoftAP drops out. I know it's dropping out because I'm sending an acknowledge UDP packet back but the packet fails to send.

Has anyone else seen this behavior?