Thought at first it was this software, somehow, but couldn't figure out how a D64 without an error map resulted in a disk of nothing but errors. Then I tried creating a blank G64 and writing that and got nothing but errors. Next I created a G64 with 64-Copy instead of Vice, and it worked just fine. Used 64-Copy to convert the D64 to G64, and it wrote just fine as well.
Further experimentation showed that formatting a G64 disk, even when created elsewhere, caused the same problem. But creating a blank disk in 64-Copy then just copying files over until it's full doesn't cause a problem. Doing a disk copy will also result in nothing but errors.
My final test run was to do everything in a different emulator. Ended up with the same results. Doing a format or data level disk copy breaks the G64 for DTC writing, but just copying over files seems to work just fine. So, writing a game's data disk that I've been playing in emulation to continue my game on real HW will probably be hit-or-miss. Would depend on how low a level the game writes to the disk If it's an unprotected disk, then I could just use D64 and do a conversion when the time comes.
that is all a change of topic, though. So, to get back "on" topic:
Can't visualize the T0 sensor, so I don't know if it has a good extension added on or not Guess I'm just going to have to live with shoving the head back past track 0 when something causes it to stop while below 0