A small hole at the bottom of the hinge panel becomes fresh air when the outer sill is cut away

Although  the sills looked fine, there was a section at the bottom of the door jamb  missing. When the outer sill was cut away it was evident that an earlier  replacement sill was unattached at both ends....frightening
Here the left  hand kidney bowl has been cut away to reveal a large hole

Left: New front lower inner panel and sill section and hinge panel welded in position

rocker repair continued