Jerkiness between keyframes

[Omnifitense]

A friend of mine is having trouble with unnecessary animations 'hidden' between some keyframes. "I dont really know, Im just doin my stuff in the graph editor and I guess somewhere along the line of creating copying and deleting keyframes and un dleting keys some weird ♥♥♥ imprint jump was created between the last two keyframes"
EDIT: Additional info: "Mine is more just those lines between keyframes being all jaged for a second or two for no friggen reason and nothing fixes is. They should be smooth lines from one keyframe to the next, not have this random jagged bumps in the middle for no reason"

[Omnifitense]

The problem appears to be that it just isn't looping properly, or again, like there's some animation hidden somewhere that he can't remove...