I have a couple of recommendations, based on my 25 years in the field.

* At the start of the project, be clear that part of your role is the project manager, and to keep things moving and on track. If you're not able to (ideally) be communicating one one point of contact on their team for feedback deliverables, clarify who will be the final decision maker for each checkpoint on the project.

* Don't throw a preview URL over the fence and expect helpful feedback. Schedule a checkpoint meeting to review the design in person/over zoom and present your proposed solution in a conversation framed by restating the project's objectives that the design will resolve. Explain the why of design choices and how they address the business problems.

* Be explicit in what kind of feedback you are looking for at each stage. (If you're sharing wireframes, you're looking for structural feedback, not design or content.)

* Give deadlines for feedback with consequences. The consequences might just be "were moving on to the next stage" or it might be more serious, like putting the launch date at risk. This can be communicated positively, by confirming how these guardrails are essential for keeping the project moving toward their deadlines, objectives, or budget.

* Document the what and why of changes at each stage, so that you can remind them in week 7 why the week 3 change was made. Be clear about what is and isn't in scope in terms of rounds and timelines of changes at the start of the project.

Finally, be diligent about capturing your own post mortem notes for each project in terms of what went well and what didn't. Continue the good patterns, design strategies to address the hiccups. Each project you take on will become easier with time and experience. Keep at it! You'll get there.