Hi Henk,
V4.3 hardware is possibly the issue. In the later hardware versions there was a resistor added which is used for hand controller detection. Without this resistor the new firmware will not be able to run detection properly and incorrectly switch into push-button mode.
To remedy this, you'll need to add a 1K resistor pins 12 and 31 of the ATMega162 (IC1) which should allow the older hardware to support the newer firmware.
If your board has the ST-4 connector attached, you should also solder a wire between pin 12 of the ATMega162 and pin 1 of the ST-4 connector (the pin closest to JP2 on the board).
Kind Regards,
Tom.