Why are the videos I make with my L920 lagging?

[WPCentral Question]

Lagging on Videos I made with my L920

Hi guys, so I've had my L920 since September of 2013, but i noticed something that happens sometimes and randomly when playing videos i made with it. The first time happened in december of 2013, i recorded my cousin's dog jumping around and sometimes during the video for 1 second the video would stop and so the sound, while recording tho i didnt notice any lagging.
This happened over again during the year, the last time was 3 weeks ago, i was recording my classmates chasing each other and at some point while they were running the video stops for like 5 seconds, so does the sound, but while recording it i didnt notice anything.
This happens not only when recording things that are moving fast, like a dog jumping or people running, but for static things too.
I'm not a genius when it comes to technology so im not able to tell if its an hardware problem caused by the times i dropped my phone, or a software problem that is, maybe and hopefully, covered by my contract.

Thanks anyway, love from italy