I must exit JExpress after I build 1 time. If I try to build a second time without exiting, I get the message "unable to create platform distribution".

Be sure that you do not have another program accessing the Build directory. For example, if you're running on Windows, don't have Windows Explorer accessing the Build directory. JExpress usually needs to delete the directory so it shouldn't be locked open by other programs during builds.
Applies to
exit, build 1 time, developer

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