I think Xavier is right:
if(keydown(5)&&this.buymode=1){
message ;
this.buymode = 0
enabledefmovement;
hideimg 200;
hideimg 201;
hideimg 202;
hideimg 203;
hideimg 204;
}
if(this.buymode=0){
enabledefmovement;
}
take the last one because if u buy from the second merchant this buymode of the first one is 0 so u can move but number 2 siabled so you collaps
u have used enabledefmovent before so it should be enough...