The pictures help a lot.

Was the original driveway a steady grade when the concrete was poured,
and has the “dip” slowly appeared over time? the dip has always been there

Just after the original concrete pour,
was the center high
and edges low?
( was there a “crown” ) A light crown so the water would got to the edges

I assume there is no wire mush in the concrete? CORRECT, bad allowance on my part, as he asked if i wanted wire fence, reboar or fiberglass reinforced. I left the choice up to him as I figured he SHOULD know best

The T junction picture brings up the issue of
periodic winter rainfall causing water inundation of that lower sect,
particularly the far side of the lower section opposite the T. The area atthe junction and below ahs bee pretty stable The section that extends to the building does have some drainage issues that do need to be addressed mainly near the front of the building.

Freeze/Thaw caused
contraction/expansion
would seem the root cause
made worse by saturated subsoil
that freezes unevenly
creating left or right transverse forces.

Cut more expansion joints,
clean out existing joints,
re-cauk.

The uphill side of the T-junction needs a drain that passes under (or through) the pavement of the side driveway. that area is actually sloped up and towards the front of the bldg. See the preceding comment

A really tricky contractor
would lay a rubber bladder filled with water along side a shifted concrete section
anchor the bladder rigidly with stakes on one side
and let an overnight winter freeze
push the concrete slab back to its original alignment.

The pressures ice can create are one of Nature’s true wonders.