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?

Just after the original concrete pour,
was the center high
and edges low?
( was there a “crown” )

I assume there is no wire mush in the concrete?

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.

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.

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 alighment.

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