Camp have you stopped using exports?
if these states are part of the statemachine, they would have to be children of the state machine and you can obtain them using a get_node()
/$
.
and we still don't have enough information because you posted what appears to be the BASE class of a number of other classes that do who knows what. there's still a billion unknown variables.
now, an idea: WHEN is change_state
executed? all you've shown us the ready
function, but claim that this problem happens WHEN changing state, meaning state is changed somewhere else.
meaning you are running this thing multiple times per frame on some other script and that could be the problem. my guess.