Understanding the Process and Its Impact on Engineers
What is the process, and why does it repel the engineers? How was the relationship between the engineers during the project completion and the client?
Motivation Through Monetary Benefits
The easiest way to motivate is to offer them a monetary benefit each time the client makes a payment since they communicated. This is fairly easy to manage as you can quantify the number of times the engineer communicates, resulting in payment. However, this will have a backlash with engineers competing on communication rather than the product or services. You surely don't want to change the focus.
Incorporating Communication in KRA
You can alternatively include this in their KRA. However, offer them some benefits as you increase their responsibilities. Identify the scope for failure and offer support if you are officially making it a part of their performance.
Career Path Development
Find a career path rather. Identify the skill required to get the amount with Business Development, hence groom engineers to become Business Managers, eventually.
Seeking Team Support
If you are not in a position to bring in any changes, be honest with your team and call for their support. Humanly seeking help will work; however, you too need to acknowledge their concerns and answer them.
Looking forward to hearing from you.