Based on the details you provided, it seems more like a problem with a slow/crappy micro sd card. Try formatting using the panasonic sd formatter. If that doesn't fix the issue, your msd is too slow to begin with. Note: back-up everything in your msd before formatting!
BTW, is it sound generated from your speakers or headphones? If you really want to be certain that it's not a hardware issue on the speakers, you can just use a headphone to see if it has the same problem. If the sound still goes out with the headphones, it's definitely something with the msd; if the sound is fine using headphones, your speakers are faulty.