Mobile camera lags when shooting 1080p video

Hi there,
I recently acquired an LG G2 Smartphone which indicated capacity to shoot 1080p videos, every time I try to shoot a video, it comes out with this lag between frames, making it look like a moment of slow motion lasting for a split second, it's quite annoying, I thought it was my mistake but, all my videos are having tiny moments of slow motion from time to time, what could be the possible cause for this and how can it be fixed?
