Bug fix on Prestashop PayPal Europe/Shipping Module

General information for the website: Bug fix
Description of requirements/features: I have Prestashop version: 1.6.1.1 with a custom theme (originated from the default theme).

I have installed this module: http://addons.prestashop.com/en/shipping-costs/20420-free-or-fixed-shipping-module.html

I worked extensively with the module developer to get the module working as required, so our installation of the module differs slightly. After eventually ironing out those issues, it was discovered that there was a conflict with the PayPal Europe module (version 3.10.2). The shipping module developer eventually resolved this (communication with the developer has always been frustratingly slow)... sort of.

The current situation is that in certain instances, PayPal seems to have the correct shipping price on the PayPal payment page, but then when sent back to the site, the total is incorrect on the payment success page. The back office shows the correct total, but shows the PayPal payment as beiing split into two payments, In sandbox mode, the notification to the buyer shows the incorrect total.

To explain, the shipping module adds a set shipping price per item for some products e.g £15 per dress purchased. We also use the PS carrier weight bands to deal with other products, so we might have one dress (shipping £15 as set by the module) and one other item with shipping £8.95 (as set by PS carrier weight bands). The total shipping should be £23.95 (£15 + £8.95).

If an order consists of only items whose shipping is dealt with by the module, then everything is fine. If it consists of only items whose shipping is dealt with by PS, everything is fine. The problem arrises when the two shipping calculations are combined. When returning from PayPal, the payment success page shows the order total minus the £8.95 shipping. The order page in BO shows the full correct total, but the payment is shown as split (see attached screenshot). Interestingly the second payment amount is £8.95 - the shipping amount set by PS. This amount is also not included on the sandbox notification which shows the shipping total as just £15.

The shipping module developer seems to think this is unique to my installation as when tested on their own installation they don't get an issue.

I am getting frustrated with the very slow responses from the developer and am not confident that this will be resolved.

I seek a developer who can find the cause of this issue and resolve it.

I have also included the edited shipping module for your reference. I can provide access to the site for assessment.
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