Speed bug when going around

[gillesdenice 0]

Hello,
Here is my problem.
I'm on FSX only
I'm making a Go-around at minimum altitude.
Before going around the 777 is in AP OFF and AT ON, altitude on MCP is 4000' (Missed Approach Altitude)

I press TOGA , Flaps 20, Positive Climb GEAR UP, Following the FD climbing to 4000'
Above 2000' i engage AP.
For the moment all is correct. My speed is around 165 kts

But as soon as the ALT Mode engage itself to capture de 4000' levelling (just above 3000'), the speed in the MCP comes every time at 220 knots and the A/T apply full thrust itself
In the real aircraft, the speed stay at the actual speed.
Unfortunately, the consequence is an overshoot in the altitude constraint too.

Please is this speed bug a known bug ?

Thanks, best regards

Gilles Menghetti
Nice, France