Randomly displays "Media Offline" in the middle of the video

I'm havin a problem where, when I try to playback the video (even if i'm using optimized media) or try to render it a random place of the video appears with "Media Offline". If i went back a few seconds on the playback and play the video on the error seems to disappear. Its bothering me a lot because im trying to edit and render the video but the "Media Offlie" message appears and i can't render it.

Im using DaVInci Resolve 12.5.6.017
System Info (Notebook):
Windows 10 64 bits
8gb of Ram
Nvidia GeForce 710m (2gb)
i7-4510U
1TB Hard Drive

The file info (the one that has the problem):
11gb disk space (~40min)
720p
H.264 Codec