So loess ia a new one for me and I read a little on it.
Do you know if any calcium was worked into the original soil and watered and graded before the sand or rock base was placed?
At this point I'd NOT recommend the grousers. It'd be worth trying the e.j.'s in the worse area.
It may be worth discussing with the contractor a combination of the expansion joints AND also reinforced concrete curb along the slab where it's moving.
These types of problems are difficult to diagnosis without knowing all the site conditions.
The reason the cleats won't work is the weight of a vehicle will simply "push it down" into the loess soil. Of course they could be designed and constructed wider and with re-worked and supplemented sub grade material (most likely wider).What I do not know about loess is if it liquefies when you drive over it. i.e. water squeezes out and carry's fines up through cracks and appears on the surface. or elsewhere. As you drive off the area the water rushes back in.
Try the correct sealing and ea couple e.j.'s and see if it's livable.
Two about 10' apart for a potential future project if it continues to displace outward.
This future work would be to remove the concrete in that section and excavate downward between 18" and 24". working and treting the removed material with calcium and/or incorporating or replacing the excvated material with good rock subbase material and compact it well (90 to 90% compaction. Then grade the top with base rock pour a reinforced slab that includes four "keepers" that are about 12" wide and deep and also run under the edges of the cut surfaces of the existing slabs. The goal is to create a seat, or abutment with little wing walls. This new slab and keeper/abutment will need reinf. steel that is tied into the slab. These keepers should be poured at the same time as the slab and the entire "unit" of 2 keeper/abutments and the slab would be monolithic.
This is something I would not let a contractor design and is should include soil analysis.
You'd be effectively creating a floating foundation/road with curbs to contain movement of the up and downhill segments.
The other concept is similar and consists of cutting 3' (more or lass determined by engineer) digging down 24 to 30" across the drive , rework the soil, pour a 3'wide reinforced footing and 12" with clete (stem wall, all reinforced with steel) and then back fill and compact therest of the trench and pour concrete or pave.
I feel for you. Through the years I've worked on all sorts of problems caused by man and nature. This one seems to have a little of each. Key is finding the angle of repose and depth to dood bearing