For months, I've experienced frequent crashes with FTM for Mac. I had hoped the new version would eliminate that, but it did not. In fact, the program crashed upon trying to open the very first file and, when it did finally open, it crashed when I tried compacting the file. It then continued crashing with even the simplest actions. The tech people at Ancestry recommended uninstalling, re-installing, etc. which did not work.
Finally, I discovered a solution. I created a new user account, logged in as that user, launched FTM and, voila, no more crashes! It's slightly annoying to have to go this route, but at least everything is up and running.
To create a new user account, go to System Preferences (Users and Groups). Click the lock icon at the bottom left, then click the plus sign. Choose a name for the new user (I used "Genealogy") and decide if you want the user to have administrative capabilities. (I chose that option since I'm actually the new user.) Create a password. When done, log out of your usual account (Apple menu, bottom choice) and then login as the new user. Launch FTM and you should be set to go! This has worked for several hours and will hopefully continue without crashing.