OPs image
This is not an adequate diagram. It leaves out critical detail.
Most servos I know have 3 wires. Power. Ground. Signal.
We need to know where all 3 are attached.
All the wires for all the components.
You mention a battery. The schematic does not show a battery or where it is connected.
You mention that you have decoupling caps. But they are not on the diagram, and we have no information in what values you used.