Hello,
It seems that right stick of gamepad (on a Xbox 360 controller, on PC) returns a inverted value on Y axis.
When joystick is up, UE will return -1.
As behavior is different from left stick, I suppose it is a bug.
This behavior has been reproduced on different computers.
Here, a simple project that display value of this gamepad axis.
Hey Begounet,
Thanks for report! Unfortunately, this is not something that can be fixed at this point without seriously impacting older projects, and there’s no realistic way to do backwards compatibility. For anyone experiencing this, though, please keep in mind that it is easily addressed if desired by multiplying Axis Value output by -1.0. Thanks for reporting this, though!
I can confirm that this is also case for an Xbox One Controller on PC.
Does this occur on other brands as well (i.e. Playstation Controllers)?
2021 and this bug is still present. Old projects compatibility should not be an excuse to have a clean code! UE is full of such bugs and inconsistencies.
2022 Still there in UE5! Old but gold. 
It can be easily fixed by editing InputSettings / Advanced / GamePad_RightY / Invert
This won’t affect code and it’s just data driven.
Seems a decent solution.