Your game crashes due to the act being invalid (the acre are the pieces of the map). Basically, you weren't paying attention when you had edited your map.
The brown squares and the plain next to the rails could be the cause of this problem.
If the cameras work fine in software other than Nintendo 3DS Camera App, the problem cannot be the cameras. Have you tried to restore a NAND Backup or a CTRTransfert?
Process ID: 26
Process name: nwm
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This error appears to correspond to a malfunction in the wireless communication.
Disable wireless and restart your console.