Was doing a test migration and it failed and reverted with this error
Command failed with exit code 1: c:\Program Files\FileMaker\FileMaker Server\Database Server\FMDataMigration.exe -src_path C:\Data\dbs\Dashboard.fmp12 -src_account admin -src_pwd *** -clone_path F:\Data\Backups\OttoFMS\inbox\jit_build_hWcwNv80yPCz\Dashboard.fmp12 -clone_account admin -clone_pwd *** -target_path F:\Data\Backups\OttoFMS\inbox\jit_build_hWcwNv80yPCz\Dashboard_otto_migrated.fmp12 -force Couldn’t open the source file because “(803): File already open but single user [extended error (20402): File permission problem].”
Source: C:\Data\dbs\Dashboard.fmp12
I created a new migration only for that file and it had no problem migrating.
testing again (turning off one large file that did a block level migration )