The error message says that he found a "<" character in the first position in the file
../../../../Source/scripts/SceneEvents_16.hx
Can you open this file from your game directory with an text editor and make sure that there is no invalid character at the beginning?
If there is no invalid character, I would check the scene that SceneEvents_16.hx file is associated to for errors. You can find out which scene that is by opening scenes in stencyl going to "Events", and then clicking on the "Code Preview"-button in the lower right corner. You can see the name of the associated .hx file then
Try to remove all events from this scene from the build (the checkbox right of the Event name) and see if it builds. If it does, activate the events one by one to track the error down to the event where it is contained in.