eBay API - auto restock of sold items

We are searching for a solution to auto restock sold items on eBay. At the moment we are using "GetSellerTransactions"-Call to get sold items oft the last 2 hours. For each result the quantity sold in the last 4 weeks is requested (GetItemTransactions-Call) und new quantity is set to 4-week-sales or minimum of 3 pieces (ReviseItem-Call). Unfortunately the current solution is not working very reliably and sometimes runs into an error (because of internal eBay error or something else). As we are selling on about 5 eBay accounts we need a solution, that could handle various accounts. Each eBay seller account should be handled with different ebay developer account. The new solution should retry quantity change if there is an error and should send an email if error consist after retry.