Low-frequency oscillations (LFOs) are a growing concern for power system stability, as they can degrade power quality, damage equipment, and even trigger blackouts. These oscillations, typically in the 0.01-4 Hz range, are becoming more unstable with increasing integration of inverter-based resources (IBRs) and the prevalence of weak grid conditions. This paper analyzes three recent LFO events observed in the North-Eastern Region (NER) grid of India. Using the matrix pencil method for mode identification and the dissipating energy flow method for source localization, the study examines oscillation characteristics, damping behavior, and origin. The results show that IBR control actions, STATCOM reactive-power regulation, generator control responses, and inter-regional tie-line interactions all influence the observed oscillations. A key factor worsening stability is the high impedance of the NER grid. Grid strength assessment, based on short-circuit capacity relative to the ±800 kV HVDC system rating at Biswanath Chariali, gives a ratio of about 2.34 in the Assam system, indicating weak conditions. With around 4.6% solar penetration by installed capacity, the study highlights the need for enhanced monitoring, advanced analytical techniques, and coordinated mitigation strategies to ensure secure operation of future renewable-rich grids.