Without hearing the tape it is hard to tell exactly what is wrong. What it seems you are describing is an effect from the tape speed not being constant. A condition that can be caused by various things but the common culprits are belts, the belt drive wheels and the pinch roller. Basicly all the parts that have rubber on them. The fact that a tape sound "clears" up once you have played it some is due to the lessening of the weight of the tape that the machine has to pull. You might try a few FF & rewinds also to unpack the tape and get it aligned on the spools. A misaligned tape on a spool creates extra drag that can affect playback. Since you say the tape sounds better on a different deck AND better once you rewound it it does appear that your home deck is probably the cause. But Azimuth is only the alignment of a head. That alignment can vastly improve a tapes sound during playback but in most cases it is a setting that can be made and then left alone. The misalignment problem described on the D5 & D6 is one that they did not match up with other decks. Not so much that they changed during playback. After having gone through a few D6's I speak from experience. A condition like that where the Azimuth is way out you can hear the other track playing backwards, but that is an extreme case. The Nak Dragon does the adjustment automatically, but it can be done on most higher end decks by hand. I'd see if you can't just borrow a friends deck first and see if the problem goes away. This problem is also more prevalent on 100 min tapes and even more so on 110 minute tapes. They were made of a thinner Mylar and are known to stretch easily, like the tape width problem described earlier. There is also a possibility that the tape has this effect recorded on it and there is no way to fix that other than load it up in a DAW and adjust pitch for each little section. If ti is a speed problem that happened during recording then it is a tough one to try and fix, but since it seems to disappear on other decks it might not be.