Hi, I also experienced those issues. Sometimes Vegas crashed and sometimes it just stopped rendering. Since I deactivated GPU-rendering I never got issues again. You can do so in the global Vegas options under “video” and the dropdown with your graphics card(s) and the option “OFF” – choose “OFF”.
Thanks Steve. I found out, that 50p suits best. Everything is smooth as I wish (just a little little bit stuttering for the interlaced-footage, but I guess that’s Vegas’ deinterlacer).