This problem is the road rut problem Elevator experienced for awhile with Jobo tanks.
We solved this problem by manually inverting the Jobo tanks in the first 20 seconds after developer was added.
then slap onto the Jobo and rotate.
The minus density is the clue which gives darkness on the positive image.
This problem almost singlehandely closed our film production for one month until we solved the problem
Agitation at starting stage of development with a twist is the answer we found.