Hmmm, both addons seem to use LibActionButton-1.0. MAYBE this is the problem?

Jamba uses the latest version of LibActionButton (as of development, not yet released) version 57. Current version of Jamba is using version 53.

ElvUI uses version 20.

When a library is loaded by two addons, the library with highest version number is kept and the other is discarded.

So what I imagine happening is that ElvUI has not been updated to use the new version of the library and is having issues. I'm not sure why the authors of ElvUI would leave this library so old for so long. Lots changed in WOW 6.0 for it to need updates (of which it has had plenty).

You might like to ask the ElvUI authors about this.