Look for the Spreader!admin
A close look at this photo identifies 3 major issues.
1, There is no sarking under the tiles.
2, There is no tile flashing between the metal/tile roof.
3, The corrugated roof sheets are not turned up.
Compounding these issues is the downpipe spreader above the lead flashing, this is the point where water flows from the upper-level roof onto the lower-level roof. During heavy rain, the flow of water is concentrated over a narrow area and the gaps where the tiles overlap are prone to leakage (especially over time as the small groves in the tile “gutter” gets worn or blocked with debris).
Sarking (the heavy-duty silver paper) helps as a secondary measure to prevent leakage, so too would a flashing between the tiles and the corrugated roof. However, as the roof sheets are not turned up there is nothing to prevent water from building up and flowing back (particularly on a low pitch skillion roof).