Since 5.2, Activiti executes processes recursively. This causes StackOverflows if processes have many steps.
Attached is a test-project which allows to reproduce the behavior (succeeds in 5.1 but fails in 5.2+). Version can be changed in pom.xml
I haven't had time to look into what exactly changed between 5.1 and 5.2 but I can do so, if asked.
Has do do something with the way Commands are executed.