Look for a pattern
One stubborn door is less informative than several openings changing in the same area while cracks or floor slopes also develop.
Check simple causes
Inspect hinges, strike plates, swollen wood, paint buildup, and hardware before assuming a foundation problem.
Combine the evidence
Openings, cracks, elevations, exterior conditions, and drainage together provide a stronger picture than any one symptom.
Next step
If several changes occur together, review foundation warning signs or call for an evaluation.