I wouldn't say it's anything wrong with form or spine if it's grouping well... sounds more like your sight is moving or something. If it's always in the same direction, and you always move your sight to correct it, then it could be an issue with your sight mount?
I really don't see how it could be consistently moving high-right if it's grouping well and you chase the arrow with your sights. If your sight wasn't moving, and you had to change it every time you start shooting, wouldn't you eventually "max out" how far you could move your sight in the upper-right direction?