Bonus Buy, Special Price List and Coupons are not working together in iVend 6.6

for example
We have the product A and Product B, C, D.
Now Product A Base Price is 1000 and special Price 100 discount.
Product B Base price is 2000 and special Price is 200 Discount.

Product C Base price is 2500 and special Price is 250 Discount.

Product D Base price is 2200 and special Price is 220 Discount.



Bonus Buy is Buy A and Get A, B, C, D on some Discount

on Top of this Coupon Discount that should be 8.4 Percent on top of all.

But the above functionality is not working fine.

Bonus Buy and Special Price are working fine together but Coupon is giving the correct discount.

Reason: Functionality is not working due to the Coupon applicable quantity. Coupon applicable quantity is configured 1 that should be equal to or more than products in transactions.