This is an issue:
"path_mapping": {
"/app/myapp/ui" : "\\\\myserver\\\\sambashare\\\\ui"
},
That path mapping does not work. And here is the workaround: mount your folder to a share with a drive letter:
"path_mapping": {
"/app/myapp/ui" : "D:/ui"
},
Would it be difficult to add native support for un-mounted paths?