After reaching a certain size, buildit crashes my Kindle Fire HDX

My city is at about 186000 population, and now my Kindle Fire HDX crashes when I try to play.  I reset the tablet to factory defaults and only had it crash once when I swiped an Amazon offer to the right instead of left. Otherwise I can play a new game for hours and hours.  When I load my saved game from Facebook, I get about 20 seconds of play and BOOM, tablet reset.

Is this graphics related or something?  Too much going on on the display, maybe?