Contract Renewals Inconsistent on Sales Orders from Web Store

We currently use SiteBuilder to allow customers to create and pay for sales orders online. We use a "download" item to represent an item group in the eStore that is replaced with two non-inventory items in a before submit user event. The script is firing as it should, however contract renewals scripts and item sourcing isn't happening consistently. When it does happen, perpetual license items are being miscalculated and represented as a recurring line item. When we move the functionality to an after submit event, the fields are all sourced, but the contract renewals scripts aren't producing the same result