Usability of a consumer electronic product (CEP) is one of the most important factors that the users consider in purchasing a CEP as well as functionality, price, etc. This has led many companies to realize new shapes of user interfaces (UIs) and styles of interaction for CEPs, ranging from modern touchscreens to physical controls and displays of any kind. Even if the general feeling is that such increased interactivity may enhance the overall user experience, the side effect is that often a CEP’s UI provides too many functions that are difficult to learn and use without referring to the user manual, leading to many usability issues. In this paper, we leverage a case study in the CEPs sector to present a novel log-based evaluation technique in the field of Human-Computer Interaction (HCI). Our technique allows us not only to keep track of the user interactions with a CEP’s UI during its daily use, but also to understand what has gone wrong during a user interaction, detecting which user actions have caused usability issues and suggesting explanations for solving them, thus providing a crucial feedback to improve the design of the CEP’s UI next version.