My setup is Galleria with a vertical jcarousel. My next and previous buttons never disable. After much trial and error, I discovered that wrap is set to "null" (with quotes) and causes a problem. The other options should remain quoted.

The javascript that places the jcarousel reads
"wrap": "null"

I believe it should be without quotes:

"wrap" : null

In addition, I think the wrap options should be none, first, last, and both. Left and right do not work.