There is a VMware Education class: VMware NSX: Troubleshooting and Operations [V6.2] which is a five-day hands-on training course provides you with the advanced knowledge, skills, and tools to achieve competence in operating and troubleshooting the VMware NSX® 6.2 environment. In this course, you will be presented with various types of technical problems. You will learn how to identify the problems and solve them through a systematic process. You will also learn about several operational, management, and troubleshooting tools.
There aren't any specific HOL labs just for troubleshooting. However, there are some elements of troubleshooting in a few HOL labs. Lastly, the best way to troubleshoot is to build a lab sandbox environment and do some break fix.