Water is coming in at this seam: (apologies for the terrible picture)

When I look at the area above, it looks like there are cracks in the seam sealant:


did a temporary fix by putting some duct tape over it to see if that kept water out, but it wasn't very successful.
However I can't recreate it by spraying water on it - it only seems to happen when it rains.
Could this area be the issue?
Is this a common problem with a known culprit?
The rain rails are not in great shape and at some point in the past, somebody has simply topped up the sealant in the rain rails to cover it up - but not in this area - at least I think this looks original, or at least older...
Any ideas?