Risk analysis of personalized medical devices, such as prostheses, is challenging due to the complexity of technological and geometrical issues. The paper undertakes a process of risk analysis for upper limb prostheses for adult patients, individualized by 3D scanning and produced by additive manufacturing. The analysis was performed to systematize the process and its steps and diagnose specific problems to achieve future devices with correct fit and function, produced in as few iterations as possible. The Failure Mode and Effect Analysis of Process (PFMEA) method was used. The results identified main process risks: the problems are primarily caused in stages, where the operator's decision or activity is to be performed, regarding socket length, offset, and suitable lining. The primary prevention activities were determined -human involvement in the decision process should be minimal, and the intelligent models should be adjustable to as many patient cases as possible. Consequently, future steps for process optimization were determined -a more extensive base of patient cases is necessary to acquire and study, to gather data for model and process improvement.