why do these bones bounce in keyframes?

so im working on a simple little animation using a tricycle.

the problem i’m having is with the bone rotation for pivot.
WHILE i rotate the bone to set the keyframes everything looks fine. once i play back the animation the bones move the mesh up and down like a soft bounce.

here are some pics. the first one shows where it’s supposed to be above the tire. when i rotate the control bone (around cursor point) it rotates everything perfectly and i create a keyframe. when i step through the frames picture two happens. the bones move down and then up to match the LOCROTSCALE keyframe.

i’m trying to figure out how to rotate along two ones because i need the seat to rotate how it is right now but i also need the bone that moving down to rotate where the axel eventually will be.

thank you.

sidenote. every piece is a separate mesh. each mesh is parented to a separate bone.

bar - bar bone
ball joint - joint bone
seat - seat bone

this works for me right now but i don’t know if that may be why im having issues.