Hi Prakarang
I tried to reproduce your case and as expected, when property is a list, it renders as elements of the list in breakdown.
When list is recognized as string, there will be 3 values in breakdown:
["nike"]
["puma"]
["nike", "puma"]
I tried to cast this list to other types and never end-up with (not set). When you look at event body, is this 2 element list available?