You can check yourself.
Rain gutter corner leaking.
Remove the old silicone caulk from the joint connection.
Ask your third guy to use butyl sealant or a tar based asphalt sealant and spread it at least 1 past the corner on each side.
If the putty completely solidified water should not be able to go through it.
To make sure that you have completely repaired your gutter pour water down your gutter then check if there is water leaking from the crack.
Corners are the places where leaks will most likely form.
Second story gutter corner leaks might not be easy to spot from the ground.
Why gutter corners are troublesome.
Repair leaking joints with silicone caulk.
One reason is because all corners must consist of at least two pieces of guttering that are affixed together.
The purpose of all rain gutters is to move water away from the base of your house.
Cut the caulk with a utility knife.
You need to remove the old caulking.
Leaking at the corners may be a sign of standing or accumulating water.
You first need to clean your gutters thoroughly.
And the seam where they meet is a natural weak point in the system.
When they fail to do.
If water is leaking where the gutter and downspout jointly connect repair the joint connection.
If you notice that there is still water leaking add putty on the area of the gutter leak.
Pull it off the gutter with your fingers or a pair of needle nose pliers.
If you have a little standing water try to dam it up away from the corner using a sponge or an old rag.
You cannot add more caulking to old.