Just my solution to this problem from a few weeks ago. I had moved my assets between folders months prior and I was receiving the same error messages stopping the packaging. Where the assets had previously been, there were 3Kb (as opposed to the proper 33Kb) files with the asset’s old names. These seemed to be acting as shortcuts(?) and were the source of the errors. I deleted them and it resolved the errors and a host of other nonfatal warnings.