Begin with the texture of the complaint. The lady struggles only with solid food and never with liquids, and the trouble is non-progressive. Solid-only dysphagia tells you the lumen is mechanically narrowed but the muscle still works, while a non-progressive, on-and-off course tells you the narrowing is fixed and benign rather than a steadily growing lesion.
That combination points to a $lower$ $esophageal$ ring, also called a Schatzki ring, a thin mucosal shelf at the gastro-esophageal junction that intermittently catches a solid bolus. The barium finding of a dilated segment sitting above a distal constriction fits a fixed distal narrowing through which solids hang up.
Test the rivals. Achalasia is a motility disorder, so it would block both solids and liquids and show a smooth tapering bird-beak, not a solids-only story; that is why it is not chosen here. Esophageal carcinoma produces relentlessly progressive solid dysphagia with weight loss, which contradicts the stable course. A peptic stricture arises from chronic reflux and also tends to worsen over time.
So a stable, solids-only dysphagia with proximal dilatation above a distal narrowing is best read as a lower esophageal ring.
\[\boxed{\text{Lower esophageal ring}}\]