One example that can be seen is that ballots that were supposed to be verified by appropriate verification documents could not be verified because the verifying documents were either lost or distroyed for some clearly nefarious reason.
https://www.abc15.com/news/state/what-do-missing-files-ballot-claims-around-the-maricopa-county-election-audit-mean 5-13-21
What do missing files, ballot claims around the Maricopa county election audit mean?
“Subpoena Non-Compliance and Password”
Fann states that Maricopa county has “refused to produce virtual images of routers used in connection with the general election.” The county Board of Supervisors have previously declined to provide the routers as well as virtual images since the traffic information on the routers include not just election department network traffic, but traffic for all the county’s departments including “sensitive data” from law enforcement.
She also says that the county has refused to “provide the passwords necessary to access vote tabulation devices.”
The passwords have become a sticking point for both parties.
Maricopa county insists that the passwords are not in their control since they are only needed by the vendor to maintain parts of the tabulation equipment software that is not directly responsible for tabulating ballots.
The Senate letter argues that the county would have been unable to conduct its own independent audit, two of which were completed in February, without these passwords.