What are some of the issues regarding the client-consultant relationship that must be addressed and managed in a successful OD (Organizational Development) effort?

What are some of the issues regarding the client-consultant relationship that must be addressed and managed in a successful OD (Organizational Development) effort? If you have been on either side of such relationship, describe the experience. Experience Example: In remodeling my apartment, we ran into severe delays with the permits as the Contractor was not clear and/or aware of the delay in lead-times. He assumed that all permits would arrive in due time. However, severe delays were caused due to the Covid pandemic and the closure of some government agencies.