Immediately after collecting the serviced camcorder, I played the tapes again at the service centre.
The black lines reappeared and the technician took the tape out and played a different tape which displayed OK. He examined my tape and there appeared to be slight wavy distortions on the edge of the tape in there region where the black lines appear.
It may be that because of the misaligned tape guide or bad tape (at the beginning of the cassette), the recording was bad and therefore the playback could not recover the time code properly to display the complete video. When the black lines appear, it seems the time code is also interrupted.
In future I will only start recording several seconds after the start of the tape.
Maybe it's just a few bad tapes as someone has suggested.