Arduino Wifi Shield R3 Firmware bug

Hello, I know I am late with this, but hopefully someone could help in fixing this:

I am using the good old Wifi shield R3 (HDG104) with latest available Firmware.
The examples are all working(!) and I am using the shield for simple http connections successfully!

So now we come to the bug: When I am trying to connect the phillips hue hub and work with it (http) it is not possible, because the connections hangs - when using the (nearly) same code with the ethernet shield everyting is ok!

After I found this in the past I now found that I could not make MQTT connections (connect fails) with the wifi shield (Port 1883) via the PubSubClient.h library. Again (nearly) the same code works perfectly with the ethernet shield.

So I assume that there is some kind of bad bug on the tcp level within the wifi's firmware.

Could someone verify this behavious and help in identifying the bug and fixing it?