Visit the rental story map to get all the basics on collecting data, navigating, and transferring data using TerraSync and Pathfinder Office. https://storymaps.arcgis.com/stories/6400358a8a3b4fa99a350b119cd903f2
This was a bug in TerraSync version 5.8 where the software would crash when trying to save a feature while a data file was open as a background file. upgrading to 5.81 or later will fix the issue.
This video covers using the Map Workspace in Trimble Connect to set up your real-time configuration for TerraFlex, setting your Project Settings, and covers the basic controls in the map.