Failures when Testing Two Projects

I have two separate applications, which are tested through two separate SoapUI projects. Both projects are set up to be entirely parallel-capable. Running each project as a whole, individually, results in fully successful tests.

When running both tests simultaneously, however, I'm seeing intermittent failures occurring in several of the test cases. At first glance it looks like perhaps some of the steps are being skipped. This seems to be limited to the test cases in which the "testRunner.gotoStepName" is being used in a Groovy script, however that is purely a correlary and may not be related.

Has anyone seen this happen, and if so, are there any suggestions on how to fix the issue?