I have an issue with Fritzbox 7490, accessing my dynamic DNS from my internal network and only with android devices. I run a couple of cameras with sighthound and access them away from home with a dynamic dns server and port forwarding, which is working perfectly. I can access the cameras fine on my note4 when I'm on cell network, but once I'm connected to my home WiFi, it no longer works. If I use the internal IP address, my note4 will access them fine. This issue is only limited to android devices as my wives S5 has the same issue, but my iPad and laptop does not.

Externally (not at home)
{mydomain}.dyndns.org:XXXX => 192.168.X.X:XXXX    (works on everything)

Internal (on Wifi)
{mydomain}.dyndns.org:XXXX => 192.168.X.X:XXXX    (fails on Android Only)
192.168.X.X:XXXX   (works on everything)

I have looked around and the only thing I can come close to is a NAT loopback issue, but that doesn't explain why Android fails, but iPad and laptop works fine, nor explain how to fix. My parents and sister have the same setup and issue, so I know it's not limited to my modem.