What angle are your downspout elbows? Until relatively recently, 90° elbows did not exist, the elbow and downspout machines did not have a setting for 90°. rather the standard elbow was 75°, even though commonly referred to as 90°.
There was a reason for that, a 75° downspout elbow generally accomplished what you would want from a 90° and there were some concerns with a 90° elbow.
Once concern is that the sharper angle would cause the elbows to clog up more easily with debris. A second concern is that the extra bend in the elbow would weaken the aluminum.
Recently, although still uncommon, 90° elbows have begun make their way to the market, initially with copper elbows. Copper is a stronger more durable metal, so concerns of the curve causing the metal to weaken were lessened.
Historically, when aluminum elbows were marketed as 90°, it was referring to 75° elbows, however we have recently seen actual 90° aluminum elbows available on for sale, typically via special order.
At www.rgdsupply.com we currently stock 2 types of gutter elbows. Our Standard 75° elbows, as well as the "Short" 30° (technically 22.5° elbows).
If there was demand for other elbows, we would stock them, but the Gutter Contractors that comprise our customer base only use and ask for these.
However if you do want 90° Copper Elbows, although not on our website, they are available via special order.