This seems to be fixed. I haven't tested what effect the switch from the euclidean to the city block distance metric had on the general seam placement, though. I assume that it doesn't make a big difference.
I did fix this with this changelog entry in libpano13:
2007-10-21 dangelo
* parser.c: reset robust estimator sigma (m parameter) to 0, if
it is not specified explicitly.
