A report, that is configured to run at scheduled times as a Flash Report in Vault, does not run at its latest scheduled date and time.
A Flash Report is triggered to run manually by a user. Every time a user manually runs a Flash Report it skips its next scheduled run.
If a user wants a Flash Report to run at its scheduled time, it cannot be run manually. If the report is run manually, the Flash Report resumes its normal schedule after the skipped scheduled run. This is not configurable and it working as designed.
Vault Flash Reports Documentation: Scheduling Flash Reports