When an LTE call drops, the root cause almost always traces back to a failure in the radio or mobility domain. The most common culprit is weak RSRP at the cell edge where the signal degrades below the minimum threshold before a handover can complete. Handover failures account for the largest share of drops, whether caused by late triggering, missing neighbor relations, or target cell congestion. Core network congestion, uplink interference from nearby cells, and incorrect parameter configurations such as wrong handover thresholds round out the top five causes.