Certified GKH Gardening Expert
Without a photo and more information on the growing conditions and your soil and water management, we can only give general information.
Severe leaf drop is most often due to water deficit/drought stress, or other extreme physiological stress.
Re-potting is initially very stressful for a plant and may not be the best thing to do when the plant is under stress already. If it recovers from whatever happened to cause the leaf drop, and it starts to put out new growth, then you can consider re-planting with a good quality potting soil. Spring may be the best time for that when conditions for new growth and root development are optimum.