Not Fully Understanding Requirements
The more inexperienced the project manager, the greater the likelihood the project manager will use his/her interpretation of the requirements rather than consulting with the subject matter experts. This can lead to misdirection in the technical approach and expensive changes in the later stages of the project.
There are underlying issues that can create this problem, the most prevalent one being the timing of when to bring the project manager on board. The 6th edition of the PMBOK® Guide discusses understanding stakeholder requirements. Oftentimes, it is not the project manager that directly interfaces with the stakeholders initially but more so sales and marketing personnel that may be required to prepare a proposal as part of competitive bidding. The project manager then inherits the requirements and may not be fully aware of the assumptions that went into the preparation of the proposal. The sooner a project manager can become involved in a project the better. When they understand what success is supposed to look like they will make it happen.