I do not get deep into subject as it might me like applying pepper powder on an open wound.
Here are some suggestions that one can give you.
A risk assessment should be performed to map out critical parameter attributes prior to validation. These parameters need careful consideration as they will form the basis for assessing the system to be validated.
Ranges used for each critical parameter should be well defined and supported by development data and or historical data. The parameters, if not adequately controlled, could affect the critical quality attributes of the product.(Seems these are not taken care)
During manufacture of an API when every you have residual solvents or impurity peaks observed are more than the limits it is deemed to be not suitable for the purpose.
Here is what the guideline says:
Acceptance criteria are established in validation protocols in order to allow the measurement of success or failure of a particular validation. Acceptance criteria should be identified from previous experience and need to reflect the key parameters that are measured during validation. For example, for process validation levels of impurities need to be controlled in line with any registered specification. Meeting the limits for these impurities consistently would be a key acceptance criteria.[/color][/b]
Deviations during validation should be fully explained in the validation report. Conclusions and corrective actions need to be described. Significant deviations that impact product quality or reject batches that fail specification should be fully ex-plained in the validation report. When API quality is jeopardised the validation should be evaluated as to whether it is best to stop the validation or amend the pro-tocol to manufacture additional batches. Careful consideration is required before this decision is made as the underlying reason for the failure should be fully under-stood and acted on.[/b][/color]
The best thing for you is just go to bench scale optimize all critical parameters and whashing parameters.You should stop the release of previous batch and also manufacturing of any further batches.