QGIS Shortest path (point to layer) start point expression in modeller

When in QGIS I run processing tool Shortest path (point to layer) … I am satisfied with the result (below picture red line).
But when I try to run the same tool in QGIS modeller, the result is different (see picture green line)

How to define in QGIS modeller shortest path (point to layer) START POINT in expression from point layer (see picture)?
I have three vector layers:

1. Start point layer (only one point)
2. End point layer (many points)
3. Network layer
   All layers are in the same coordinate system: EPSG:3301