Hundreds of cases have been reviewed by the National Crime Agency after two major money-laundering inquiries collapsed due to problems with warrants.
The body, Britain's version of the FBI, announced it would review a slew of cases in August 2015 after an Old Bailey trial collapsed and the NCA received a dressing down from judges over a bug-planting raid.
On Tuesday the NCA said that 326 cases had been reviewed for potential deficiencies, with "potentially significant" issues found in 51 and "minor" issues in 242.
The 51, which had errors such as failing to specify the items sought on the face of the warrant, were picked out as having a "significant risk they could result in challenges to the lawfulness of retention of the material seized".
However, since the collapse of money laundering probes Operations Heterodon and Enderby, no other cases to date have collapsed, the NCA said.
Investigators had asked three defendants to consent to the NCA continuing to hold seized material and they had all done so.
Head of the NCA Lynne Owens said: "The review has not identified any bad faith or misconduct on behalf of any officers. This is more about precision and detail in drafting than anything else.
"I'm pleased to say that since the original two cases, we haven't lost any cases as a result of failure in warrants. The agency continues to be deeply proud of our conviction rate."