I just noticed some very evident chromatic aberration on the garage door which should not be present at that small enlargement. That might mean there is something wrong with the scanner or the scanning technique. I can't believe any lens can have that level of CA. How CA relates to lack of sharpness I don't know, but it might be that a problem (such as bad planarity) shows as lack of sharpness and as CA, and by solving one, one solves the other. Maybe the film was placed on the flatbed on the wrong side? Maybe some non-noticeable dirtiness? Maybe the scanner has an alignment, calibration procedure which must run from time to time?
Just some thoughts...
PS On seeing the scan again, and seeing that it is scanned at 2700 ppi, not that small an enlargement the CA seems a bit more forgiveable, but nonetheless it is quite apparent.