I have two tools that need to packaged into a single GPK in ArcMap 10.6.1 (with Runtime access enabled).
The tool executes with no problems/warnings, and I can package each result on its own: e.g. create "tool1.gpk" from first result, and "tool2.gpk" from the second result.
However, when I Add Result in the package creation and run it, I get the general "999999" error. (It looks like it's happening towards the end of the whole process, but that's completely a guess on my part.) No errors in Analyze, just a failure to create a multi-result package.
What should I be looking for while trying to resolve this problem and get both my results into the same GPK?