Historically, due to "bad batch" concerns, tapes within a given case have come from different production runs.
That way if you do have a tape with drop-out problems, the entire case should not have them.
(I don't know if this practice is still followed.)
So, it could be that you found a "bad one" in the lot.
Or, it could have been a miss-thread when the tape got loaded in the camcorder.
You know what; it is quite possible that the video tape player head is out of alignment. This would explain why the camera didn't give any indication that the tape was bad... the tape is probably not bad... it's more than likely the tape player is misreading the data off the tape (because of alignment issues.)
This has happened to me before.
The best way to prove this theory, is to actually have the camera original tape played on another tape player and check, frame by frame, where the drop out is observed. If the still (paused) image shows no dropout, where a dropout is seen when playback is executed, then the tape is OK.
Yes thanks,trouble is the originals are on the other side of the world,and still no real info from them,which makes me think,as has been the case with all other so called camera problems,its a cock up at their end!