Answer
A ring 'popping out' under nominal load is usually due to 'Incomplete Seating' or 'Radial Interference'. If debris is trapped in the groove, the ring cannot fully expand/contract into the bottom of the groove. Another cause is 'Chamfer Interference' on the mating part; if the mating part has a large chamfer or radius that contacts the ring, it creates a 'Radial Force Component' $P_r = P \cdot \tan(\theta)$ that pushes the ring out. Diagnosis involves checking the 'Contact Pattern' on the ring. If the wear marks are only on the outer edge, it indicates the ring was not fully seated. Corrective actions include cleaning the groove, reducing the mating part's chamfer, or ensuring the ring's free diameter provides enough 'Preload' in the groove.
