D6 is Redundant and Add Judgement at D5

Verification versus Validation in 8D Problem Solving
Ondrej Durej, Management Consultant, Slovakia, Member

You must realize the difference between verification and validation:
Roughly speaking VERIFICATION means that you will try whether an intended corrective action works and VALIDATION means that you will confirm that it really works long term.
Verification of a corrective action should be done before or during its implementation. Obviously you will not implement an unworkable corrective action.
Validation of a corrective action should be done after the implementation of the corrective action to confirm its effectivity (that it really works) long term.

D5 and D7 are very different
Theo Villella, Business Consultant, United States, Member

D5 and D7 are very different. D5 happens before the solution is implemented; it is the work done to ensure the solution will be effective and permanent. D6 is when we implement it. D7 is sharing lessons learned to prevent reoccurrence everywhere it may apply. Operative words permanent then pervasive to ubiquitous.