Ok, so I have about 60 tests in this project. I have a lot of issues with instability with larger test lists, especially when running the tests remotely on the run-time licence, so I almost have a test list for each test case and need to run them individually. When loading elements on TS startup I think I have about 345. If I could add all the test cases to a handful of lists and reliably run them, the delay would not be much of an issue, but seeing as how I get a lot of false positives that way, it's not really worthwhile. Locally the tests run much more consistently.
After seeing your post I realised that I was indeed running a rather old version, in fact the last 2015 release. So I've tried updating both Test Studio (Web and Desktop) and the run-time to current versions, 2016.2.630.1.
However, the update took med from bad to worse, as a whole new problem was introduced. Now the application that I'm testing closes mysteriously after the first step is run. I don't have enough technical expertise to evaluate why this current problem appeared, so I will ask a developer to look at it tomorrow and update the ticket.