You are employed as a TAE on a project to build a purchasing system. The main requirements for the system are:

1) Allow users to enter details of items that they wish to have purchased and, from these details, create a purchase request.

2) Take each purchase request through a workflow that will allow the requestor’s line manager to approve the request, reject it, or return it for clarification/modification.

3) Forward approved requests to the Purchasing Department.

4) Allow purchasers to find the best available supplier and place the request on that supplier as a purchase order.

Requirement 1 has now been delivered and has been satisfactorily tested manually. In parallel, you have developed a TAS so that functional suitability testing can be automated.

The functional suitability testing of Requirement 1 has now been automated as fully as possible. A change to add audit logging of user activity is planned but has not yet been made. After a small change to the UI code, the last regression run contained a significant number of unexplained test failures. At the point each test stopped, the actual and expected results showed no discrepancies. In each case, the run was able to continue with the next test in the suite. Preliminary investigation showed that the points at which these tests stopped had nothing obvious in common.

Which option below contains the BEST next steps to investigate this?