"Backdating" or "down versioning" an asset always has the risk of changing the compliance rules that the asset must pass to become usable in Trainz. An asset that passes the compliance tests for build 5.0, for example, may not pass the compliance tests for build 4.8 or 4.6 and will be reported as faulty. The same can occur when an asset is up versioned to a higher build number.
Check the status labels of those altered assets in Content Manager.