Stick a group button on your plot and check it can be selected.
Place a gang of 2 lights nearby the group. The gang should have 2 rows 1 column and run vertical on the plot.
Select just the gang and not the lights and make it wide enough so the cursors that adjust the size cover the group select button. This won't have an impact on the width of the gang as its only 1 column.
switch off edit gangs and try to select your group.
You can't.