Good to see everyone sharing their experience here.
Myself did it on Magus Quarters. I actually just build strong defenses and let it run. Took an hour break at Wave 16 and on wave 18 left my PS3 on all night as I slept, went to work and come back for lunch break (around 14 hours in total). Started wave 19, and finish it to unlock my final and plat trophies. And its played offline of course.
Like Heisenberg said it may be random despite letting the ticker finish because some of my other buddies did similar stuff but still having the freezing issue. Can't really tell coz i dont think anyone's gonna research this.
Hopefully the upcoming patch will fix this glitch as it is the top 3 comments given to Trendy to fix.