There is nothing wrong with the ALAC (Apple Lossless) files, which were created with Apple's open source library.
However, some players or devices might have compatibility issue with ALAC files in multi-channel and/or with sample rate other than 44100 Hz. For example, iTunes is known to have problem dealing with multi-channel ALAC files. It does support Stereo ALAC files, however.
So please stay with Stereo and 44100 Hz for best compatibility, or just switch to another player that support ALAC format better.