First off - There should be no issue with washing your OA/water soluble boards with the other customer's no clean units provided that the recipe being used has been validated to effectively clean each product.
If your supplier is using a batch system, the wash time, temp and number of rinses should be something they can show are based on study or at least MFG'r recommendation for the cleaning solution.
Has the supplier verified that their machine is functioning properly? Spray bars spinning? Wash solution is within correct % range? Chamber is not overloaded causing shadowing?
Does your product have difficult to clean areas? Low standoff components such as BGAs, LGAs, QFNs, jam nut receptacles?
Are there post wash hand add steps (at supplier or in your own facility) where the wrong flux or too much flux is being used and not activated by soldering temps?
Does your supplier have the capability to perform a ROSE cleanliness test that you can compare your results to?
reply »