Problem with custom Group Pricing and Discount Coupon

[mvstudio]

I'm having a serious issue with one of my stores and I can't figure it out. A few months ago I wanted to disable the use of discount coupons for group pricing. I couldn't find the solution but one of my programmers, I'm afraid no longer working with us, did find and apparently made the change without my knowledge until today.

I've been offering my group discount customers some unique discount coupons for extra saving, thinking they would be able to use them along with their group discount. One of my group pricing customers tried to use the coupon today but the discount is not reflected on the total, despite giving on the checkout_payment page a message saying the coupon was added successfully to the order.

Using my testing account I was able to confirm as a regular client the coupon does get discounted, but the moment I change the switch the account to the group, the coupon field and the discount disappears from the checkout.

I've checked up and down and can't figure out what was modified that could potentially break the shopping cart in this manner.

The files I've checked so far are:
modules/ot_coupon
modules/ot_group_discount
common/tpl_main_page
common/html_header
common/tpl_header
templates/tpl_checkout_payment_default
and they all seem to look ok. I've removed/replaced them with the original ones and nothing changes.

Does anyone have any idea what should I look for and on which file?

I've looked throughout the forums but I couldn't find anything.

Thank you very much for any help.

[mvstudio]

After hours of checking we finally found the problem.

For anyone encountering a similar situation check the sort order of the modules in modules>order total.