Accessed CA's 14.4 Sandbox, this morning - 'copy from template' works, there, without giving this error message.
Still have the issue in our 14.2 setup - so, the questions now is: Was a fix created, contrary to the message in other thread?
Relieved that feature is working in 14.4 - before continuing our own troubleshooting, would like to know if this problem required a fix, or should we continue looking for something wrong in our dataset, for something that we can correct in our 14.2 environment...