Same issue here. Please post outcome of ticket.
I have the same issue whereas I have all small items shipping in one box.
If I choose:
1 item A that is 0.5 oz it quotes $1.95 (the minimum quote)
If I chose:
3 item A's which is 1.5 oz it quotes $5.85 (not correct)
If I chose :
1 item A 0.5 oz
1 item B 0.5 oz
1 item C 0.5 oz
for a total of 1.5 oz it quotes $1.95 (which is correct)