Voids and settlement have causes
Soil consolidation, poor original compaction, water movement, downspout discharge, leaking drainage, washout along an edge, backfilled utility trenches, and frost-related movement can contribute to loss of support. Clay-heavy local soils may hold water and move seasonally. Lifting without discussing the cause can leave the same water path active beneath or beside the corrected panel.
Look for gaps under exposed edges, eroded soil, animal burrows, washed stone, nearby roof runoff, and cracks that open toward the settled area. Mention recent plumbing, utility, landscaping, or drainage work. Not every void is visible from the perimeter, but the surrounding clues matter when deciding whether the slab is a candidate and what other correction may be needed.