According to the user's guide, found here:
http://www.retrevo.com/s/JVC-HR-S780...19ag217/t/1-2/
manual tracking is available:
Manual tracking adjustment
If automatic tracking cannot eliminate noises well during
playback, use the manual tracking following the
procedures below.
c You can also use the manual tracking during slow
motion playback (Z pg. 29).
1 Activate manual tracking
Press channel up and channel down on the front panel at the same
time during playback.
2 Eliminate the noises on the TV screen.
Press channel up or channel down (or CH + or CH – on the Remote).
Press it briefly for a fine adjustment, or press and
hold for coarse adjustment. Watch the screen and
continue adjustment until optimum picture and
sound quality are achieved.
3 Reactivate automatic tracking
Press channel up and channel down on the front panel at the same
time. The automatic tracking becomes active again.