With a test wide field image cube, if the pv cut is sampled with fixed pixel separation, the origin of the offset axis is correct as

However, if we simply increase the pv cut of the above example so that it is sampled with fixed angular separation, there seems to have an offset in the offset axis of the pv image as

We can see the origin of the offset axis does not overlay with the peak emission of the central gaussian source.

@pford do you have any idea on this? Could it be due to the precision issue when converting pixel coordinate to world coordinate in such noticeably distorted sky field?