Washington (CNN) The US Air Force's failure to properly document Texas gunman Devin Kelley's 2012 court martial conviction for assault on his wife and their child in a federal database used for firearm sale background checks reflects a systemic problem with the Department of Defense's system for sharing critical case information with the FBI, several former FBI and military agents told CNN.

Air Force Secretary Heather Wilson said Thursday the service will continue to review the case of Kelley, who killed 25 people and an unborn child at a Texas Baptist church Sunday, along with others in various databases for signs of mishandling, but she said she was not aware of past problems related to sharing criminal history data.

Yet several former military investigators told CNN that top officials have not only known about problems related to criminal records handling within the Air Force Office of Special Investigations for years but that they stretch across all the service branches.

"I am not at all surprised by what happened," one former OSI special agent told CNN. "I've seen a lot of the same, and some worse when it comes to how cases are handled and documented."

The FBI references three databases -- containing tens of millions of records provided by local, state, tribal, and federal agencies -- as part of the National Instant Criminal Background Check System (NICS) -- the process used to determine whether an individual is qualified to purchase a fire arm.

The Air Force and other military services are expected to submit initial case information -- including fingerprints -- through an internal system that then relays data to a database called the National Crime Information Center (NCIC), which should show up during a background check.

Additionally, military investigators are tasked with submitting a document to the FBI that details the outcome of a case once it is officially closed. The details from that form are then entered into another database called the NICS indices by the FBI. Because only some of the information from military criminal cases is made public, the services are generally responsible for their own oversight.

The Department of Defense has had a long-documented history of issues when it comes to transmitting relevant criminal information to the FBI and the databases -- a problem that was raised as early as 1997 in an inspector general report.

Former military investigators said OSI still relies on agents entering case information into shared databases by hand -- a labor intensive process that has produced a severe backlog of files that can "sit in a desk drawer for years" without being added to the system.

The military's investigative offices are measured by their handling of active investigations, not closed cases, one current OSI agent told CNN, adding that the detachments are often overwhelmed by active investigations and a backlog of cases.

Another former OSI agent described an instance in which a detachment commander hid boxes of case files in the ceiling tiles prior to an inspection because they were so old and entered incorrectly, which prevented them from being used in background checks.

In addition to an overwhelming backlog of cases, former and current military agents also said that many of the case files that do get sent to the FBI are often incomplete or inaccurate.

"The system as it is now is personality dependent, which is obviously irresponsible and broken," a former OSI agent told CNN, noting that accurate recording of case details depends on the discretion of individual case workers

"If agencies aren't submitting the correct data, that threatens the whole system," said Tom Bush, a former assistant director of the FBI's Criminal Justice Information Services (CJIS) Division, which oversees NICS.

In the grand scope of data referenced during a NICS background check, states and local agencies have much more to share than the Department of Defense, but any gap can create serious consequences, as the case of Devin Kelley shows, according to Bush.

"That's your worst nightmare -- that someone slips through the cracks," Bush said. "Unfortunately, sometimes it takes a tragedy to reveal where the fix is needed."

In 2007, Congress passed a law that required all federal departments, including the Department of Defense and its criminal investigative organizations, to share information with NICS that would prohibit individuals from purchasing firearms.

Stephen L. Morris, who retired in February as assistant director of the FBI's CJIS division, said the FBI does not have the capacity to ensure that all federal agencies accurately and consistently share all of their records.

He said the FBI can offer recommendations but federal agencies must develop their own internal processes to follow the law and should penalize those who fail to do so.

"There's a lack of accountability. Congress can pass laws to mandate that information is passed along, but record sharing is a complicated process, and if there are no consequences for not following those laws, what's the point?"

A spokesperson for the FBI said the agency's CJIS division reviews agencies that access its databases every three years, but those reviews focus on information that has been voluntarily entered.

"The audit scope would not seek to identify information that the Department of Defense or its branches chose not to voluntarily share for NICS purposes," said FBI spokesperson Steve Fischer.

Government reports show the military has a history of inconsistently sharing information with the FBI.

2015 report by the Pentagon's inspector general found that hundreds of fingerprints and final case reports held by the Navy, Air Force and Marine Corps were not passed to the FBI's criminal history database. The branches had a compliance rate of about 70 percent, according to the report.

In 1997, the inspector general also found that the military's criminal investigators were repeatedly failing to submit criminal history data to the FBI and concluded they "placed little emphasis" on that reporting.

The Pentagon's Office of Inspector General announced this week that in addition to a review of the handling of Devin Kelley's case, it will broadly review the policies and procedures for submitting information to the FBI for entry into the NCIC database.

Lindsay Nichols, federal policy director for the Giffords Law Center to Prevent Gun Violence, said that mounting evidence suggests some offices within the Department of Defense are out of compliance with the federal law on records sharing, which she said can have life-and-death consequences.

"This is a systemic problem that authorities have known about for years but it has not been fixed," she said.