What kind of SDHC card are you using? I was reading in the manual and in other sources on line that you need a class 8 or higher SDHC card to do longer takes. Haven’t went out and bought one yet to test, but the numbers logic kind of makes some sense.
In the meanwhile we’ve been doing a sync slate at the beginning and end of takes to have two sync places.
seems to be a quick fix, but nonetheless a hassle.