This doesn't just happen when in "catch a pokemon" minigame mode. This happens at all screens. The game was programming to expect full, 100% network connectivity, and if it loses that for even a brief moment, the whole thing comes crashing down, requiring a full kill and reset.
Can someone explain this? Isn't the value of a game in the playing of it? If a millionaire could pay to have hundreds of Pokemons spawning in their living room so they can get more points than anyone without leaving the house, what would be the point? If you're having fun playing with your girlfriend, but don't have much free time, why would paying to catch up matter? Did they design it to be limited gameplay, where you only get a teaser if you don't play it all the time, requiring that you buy things in order to get any real gameplay time out of it?
The real killer? I love the idea of this app. I'd probably end up spending a bunch of money on it if I kept it around for a couple months, because I don't have the time I need to play it the free way. It's fun (or it at least scratches that grindy type itch), and it's the only game I've ever been able to play with my partner. I'm on the verge of uninstalling right now though, because every time I get the chance to play, the app dies in my hands.