ZXBox space key input problem

[dma]

Hello,

It seems space key input is problematic on ZXBox (I am using it on Sansa Fuze v1).
I cannot get past title screen on many games which need space key to be pressed.
I tried either virtual keyboard or keys mapping (predefined and custom), but no luck. Of course Kempston mapping is deactivated.
It happens on Stunt Car Racer and Juggernaut.

The only game which I can get past title screen is Micronaut One with Kempston mapping activated, as this one works with this joystick model.
So I then tried reconfiguring keys in this game, to test keyboard input, and indeed space key press isn't responsive, when other keys work.