You can use Console to check for crash logs titled Vectorworks listed on the left hand side under DiagnosticReports.
Better still, when VW crashes, open Console, ensure you have "All Messages" selected on the left-hand side, then type "vectorworks" sans quotes into the search box top-right. You should see a few messages - and probably the same messages repeat each time VW crashes. Take a screenshot of these messages and post them here (use command-shift-4 to take a screen shot). An example is below. Clicking the paperclip icon next to a message opens the relevant log, and will further detail the crash.