Actually you are right, they really moved with me to my other place in SG.
The dropping of coins plus marbles. Earlier when i stayed with my parents new place right after NS. My dad went up to complain of the playin of marbles, etc. Turned out the couples son passed away a month ago... We still hear his toys being pushed around at night and even once when the parents moved out. Fortunately, in Johor (touchwood), no such noises.
The lighting part could be a misconnected cable, etc. Had this once, my wife turns on the switch in the master bedroom, the toilet light at the common toilet turns on. Turned out to be a cable issue.
Another time even better, electrician wired lights to a ceiling fan (go figure) so whenever one turns on the fan, the lights will go on as well.