The package wasn't able to finish and return an error code to PDQ Deploy. By default, PDQ Deploy returns either a success or error code depending on the final disposition of the package. If that process is interrupted and not allowed to complete, say the process is prematurely shut down on the target(s), this is one possible error.
This can be due to network or disk issues on the target machine or could be a bug in PDQ Deploy.
Try the deployment again and if it still fails then contact email@example.com for assistance.