Promo works fine on order process but works oddly on submit checkout

I have create promo code for giving discount 10% OFF. When I use it on order process, it works fine.

For example, the billing is 180, then disc is 18 (10% from 180) and total become 162.

giga10off.png

But when I click submit on checkout, invoice generated different amount.

For the same example, the billing is 180, then disc become 20 (?), and total become 160.

invoice-promo-10-off.png

When I login to client area, I see on menu Services -> My Services, it show the correct discount

my-service.png

But when I see on menu Billing -> My Invoices, it still show the wrong discount.

my-invoice.png

Is this a bug?

I use WHMCS 5.2.7

Thanks

Diginiq

Attached Images

• giga10off.png (31.6 KB)
• invoice-promo-10-off.png (27.3 KB)
• my-service.png (24.7 KB)
• my-invoice.png (23.5 KB)