Hi Pinball G,
Try going to Diagnostics and running through the switch tests, you could have a shorted/dead diode which may trigger 2 switches at once.
print out the switch matrix and run through each and tick it off.
if you find that more than 1 come on at a time I can assist. if all ok try the switch edge test and tune each of the drop target leafs and the stand up leaf also.

thanks mate for the offer. Unsure about your advice. This is a 1980 game and I'm only aware of one test I can do which is like a switch edge test. I did try all switches and the work ok although the rhs standup has a switch value but the target in question has a switch value of zero. So if I drop the drop target it gives a reading and then when I activate the standup, it gives zero.

My problem is a little intermittent, you can drop the  drop target and a phantom standup activation my take place in a second or after a minute or two or maybe never  as you can lose the ball. I have repeated hit the right flipper and t may activate which is the only time I can say a device may have attributed, but then maybe its vibration??? I'm really unsure on this one.