I suspect that the "white residue" between the coax cable jacket and connector is the result of environmental damage but I could not confirm it yet. Did anyone have a similar issue and if so what was the cause? Thanks, AL6B.
It appears to be typical moisture ingress. The joint between the coax and the connector is not inherently waterproof. A damaged jacket can also be the source of moisture ingress. Normally the connector to coax joint must be covered with a self sealing adhesive tape or heat shrink tubing with an interior thermal adhesive in order to protect it from the elements. If the connector is a PL259 the entire connector should be dressed similarly since it also is not waterproof.
Unfortunately, the jacket corrosion also impedes the proper flow of RF current. You may be able to cut off a foot or two and if there is no further corrosion, you can then install a new connector and waterproof the assembly.