If for some reason the parietal cells of the stomach epithelium become partially non-functional, what is likely to happen?

Parietal cells (also known as oxyntic or delomorphous cells), are the stomach epithelial cells that secrete gastric acid (HCl) and intrinsic factor. Hydrogen ions are pumped out of the cell into the canaliculi in exchange for potassium ions, via the H+/K+ATPase. As a result of the cellular export of hydrogen ions, the gastric lumen is maintained as a highly-acidic environment. The acidity aids in digestion of food by promoting the unfolding (or denaturing) of ingested proteins. As proteins unfold, the peptide bonds linking component amino acids are exposed. Gastric HCl simultaneously activates pepsinogen, an endopeptidase that advances the digestive process by breaking the now-exposed peptide bonds, a process known as proteolysis. Hence, if for some reason the parietal cells of the gut epithelium become partially non-functional, protein digestion in stomach would be compromised.