Events 4 & 10
Are you aware that the events run FPS times per second ? .... top-down.
One run trough the event sheet we call a 'tick'.
So your game starts. And in the first tick it creates those ships depending on player(1/2)choice.
The next tick, player(1/2)choice is unchanged. Hence, those events are still true. And it creates again those ships.
The next tick it creates more ships ...
And more .... and more ... and more ...
Run it in the debugger and watch the object count run out of control.
Easy solution ...
or 1/ add System > condition> 'Trigger once while true' to each event containing that 'player(1/2)choice = ?" conditoin.
or 2/ just change the value for player(1/2)choice to something like 9999 after it is for the first time used
or 3/ deactivate both groups after they ran once ... System > action > 'Set group active'