I suggest you check the ULS Log firstly to see the detailed error message, it will help us to find a solution to resolve your issue.
For SharePoint, the ULS log is located at the path:
C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\15\LOGS
Yes, I tracked it down.
Those ULS logs are too deep, but that's another story.
Sadly, the error message displayed has nothing (zero) to do with the issue.
It was use of a JS variable with having declared it.
Nothing to do with strFolderName, etc.
Wish the JS tooling would mature some day, it has been a decade plus, it is not just here but everywhere that JS error messaging and tracing and intellisense and such like is just dirt compared to C-Sharp.
But, I hacked my way through it and, FWIW, you were right-- ULS log is the place to go-- but that sucker is deep, too deep, I have to figure out how to scale back the things being logged-- problem is that I do not want to miss anything important. Oh well. I will hack my way through that too, I suppose, eventually.
Still, I am liking SP 2013, it is pretty cool.
I suggest you can create a new site collection and then recreate a new docuement set to test whether it works.
Actually, creating a new site collection was not necessary for me.
Still, I wish those errors that SharePoint shows would be a big more on-target and descriptive, because "strFolderName" had nothing to do with the actual error.
Thanks for your sharing and feedback !
Which file? what change?
First, please be sure you understand my answer above.
The problem that I had was with MY code, not anywhere else.
That is, it is because MY code was broken that caused the error.
>>> Which file?
>>> what change?
Overall, I think in my case it was that MY code caused the whole page to break and stop processing, therefore the strFolderName (and it's surrounding logic, all of which is part of SharePoint itself) never was properly run and broke as a result of MY code having stopped processing on the page.
So, it seems to me, that is the full story behind what happened in my code.
I hope my story helps others, etc.
-- Mark Kamoski
I am troubleshooting a customer issue, The information will definitely help. Once I resolve it, I will post my findings and solution.