During testing migrations I found that applying of ScanModelUpgradeV5 drops all data from all tables of plugin, including Scan, RefScan, RepoScan as like as InvalidLine, ValidationRule.
First 3 are probably cleared by intention, but this make useless previous data migration, which tries to reuse existing InvalidLine table data for new Scan Dashboard, so it's very questionable solution.
But what is more important, this migration also drops user-created rules (ValidationRule data) in addition to scan results, as it supposed by ActiveObjects.migrateDestructively method design, see additional description here.
I'd suggest to rollback or rework these migration asap to not damage existing user data.
Bitbucket 6.4.2, Postgres 12.2