What's causing my games to sometimes exit to the homescreen?

I have a Sony Ericsson Xperia Ray. When i first bought the phone, it came with a 4GB class 2 microSD without a brand name. I could play games without problems and it was pretty stable. Then I bought a cheap 32GB microSD without any class. I moved my files from the old card into a new one by copy-pasting them. When I play games (mostly big-sized games) the games will sometimes suddenly crash to homescreen without any "force close" option. Then I thought it was maybe because of the cheap microSD so I bought a new Transcend 32 GB class 10 microSDHC. It is fast enough for HD games, and I'm satisfied with it, but the same problem happens - games will sometimes crash to homescreen. Is this because of my storage space? Maybe I installed too much stuff on it? I have 80 MB free space. Maybe this is the cause? My phone condition: - Rooted - No other modifications applied.