Well the button does not stick or feel strange in any way. Think I'll have to explore into the console to see what's wrong. Also short while ago meddled with rear seat, might have caused a wire to frail. BTW if trunk is locked, this won't happen (and I won't hear the trigger go).
In general I noticed that the wires on most 164 looms are quite thin, at times I'll get the occasional gremlin that comes and goes, warning light, erratic gauge etc. Need to find time and energy to sort everything out, when I got my B the power windows (ALL of them) didn't work, and interior lighting, which I got fixed. still got the A/C stepper motor and now trunk.