The issue has been fixed with Apple’s MacOS High Sierra 10.13.4 Beta (17E139).
You can try out the fix by updating your machine to the beta update from Apple.
Let us know if the issue is fixed for you after aforementioned High Sierra beta update.
An error occurred while saving the commentKathleen Herr commented
My files are contained on a server and InDesign will not package the files. I also get the warning that InDesign is unable to access the server on which the file I am attempting to package resides. The only work-around I have found is to create a new folder on my desktop, save the InDesign file to that folder and package from there. Seems to work, but a real time waster. Super frustrated right now.