Strange Timecode Stutter with New HDV Camcorder

We have been recording an extensive oral history collection since 2000. We started with mini DV, went to DVCam, and have been using HDV shot with 2 Sony HVR-V1Us for the past 7 years. We have over 1100 hours in the collection, and we use FCP 7 for our editing work. We've been very fortunate not to have run into any major problem in the past. Last November, we retired the V1s and bought a new Sony HVR-Z5U. So far, we have shot 10 tapes total on 5 different occasions. Three of the tapes have a strange Timecode issue.

We first noticed it doing a Log & Capture. One 2 minute clip suddenly broke into 2 clips with about 6-7 seconds of video lost. When we looked at the original tape closely, we saw that the Timecode just freezes, and then continues about 2 seconds later. It does not reset to 00:00. We tried playing the tape on a separate deck and the camcorder itself, and the results are the same.

This past weekend we shot 3 events for a total of 5 tapes. Two of the tapes are showing the same problem. On the first tape, it happens in the middle of a 6 minute clip. On the second tape shot the next day, it happens within a few seconds of the first shot after color bars. As before, the timecode seems to freeeze and then jump ahead a couple of seconds. In all the upload attempts, FCP breaks the clip and loses 6-7 seconds of video. Once the entire tape has been uploaded, the Media Start and Media End on the clips with the timecode issue verifies the loss of the 6-7 seconds.

Yesterday, when I realized this happened, I set the camera up and recorded about 25 of clips and did an upload successfully with no timecode problems. On the 10 tapes shot so far with the new camera, the problem is on 3 tapes shot days apart.

I guess it could be a problem with the tape. But we buy large amounts of Sony HDV tape from the same vendor we've used for years.

Has anyone else run into this or a similar issue?