Engineers and product managers often have differing perspectives on what is important in a project. Engineers are typically more concerned with the technical aspects of a project while product managers are more focused on the business end of things.
Engineers tend to dislike about product managers is that they need to work within their constraints, which can be frustrating. Engineers feel that they could do better if they were given more freedom to do what they wanted. Product managers, on the other hand, might find engineering tasks tedious and time consuming.