If the batch file works outside of LANDesk (always test), then we will have to know what error it is throwing (error code in the console, and upload the sdclient log file. Since you are running usmt from a share make sure that domain computers has read writes to execute the exe. Also since you are dumping the files onto the share make sure that domain computers can write to that path. LANDesk runs as local system account.
I also notice you are using a username variable. As LANDesk runs this as local system, it won't work. Make sure that you have set the account setting for this to use the current user and make sure that user has the rights to read and right to the location you specify.
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The batch command works when run on the client computer, I also converted the batch command to EXE and MSI and both are working as normal with the client computer when executed.
I manage to get it running on package only in MSI but it skip the process of scanstate on USMT... Right now i have added temporary on the Launch pad for your user to use and it works just fine.
Let me know if you guys have further advice.