this issue is not something that can be determined via email. it most likely will require a qualified network person to locate and resolve the problem.
you might want to look at the z240 network permisions and also the file share settings. do you run a virus program?
i would use a HP restore disk for the z240 on a test z240 and see if it has the same issue (i suspect not) if you don't have a HP restore disk, use a generic windows 10 image from microsoft, and again i suspect it will not have any problems.
if either of the 2 methods above work, then the issue is in your custom image