I have done some reading around coolants.   Propylene Glycol is only used because it is less toxic than ethylene glycol. It is less effective as an antifreeze. Propylene glycol oxidises when exposed to air and heat, forming lactic acid. It must be suitably inhibited to prevent corrosion. Biological fouling also occurs with PG.   The ONLY evidence I have been able to find about Organic Acid Technology (OAT) and Hybrid OAT (HOAT) causing problems was with coolants containing 2-