I have this problem as well, for well over a year now. I'm using Vectorworks 2018 on a Macbook pro running Sierra. Vectorworks has become almost unusable. Simple actions like editing text cause terrible lag, which gets progressively worse during each session. Every hour or so Vectorworks will crash or freeze, and I often have to reboot my computer. I am only using the software for 2d construction drawings, using the most basic features. I paid over $7,000 CAD for this software so I'm extremely angry and disappointed. Vectorworks has never managed to address these issues. I see dozens and dozens of forum posts complaining about the same issues, and never any progress indicated or solutions provided. At this point I am on the edge of going back to Autocad, at least I know that it's stable.