I just used BRAND NEW sony premium DV tapes, shooting with a Z1 and experienced significant unrecorded footage. I was shooting over 2 days outside in intermittant drizzle and cold weather. My camera was covered however with a raincoat. After reading the previous discussion on tape malfunction I am equally confused on why my tape was unrecorded.
I did notice that some of the tapes appeared to be slightly thicker and did not drop into the loading box as easily as other tapes.