I made a SEX Video for you - Strange Electronics eXperience:

Measuring the voltage between the batteryholder's plus and the IO board's plus when Servos are moving - the voltage over ONE connection (wires, switch, pin) is about 0.1 to 0.4 volts.

Assuming the minus side is the same then there are up to 0.8 volts eaten by the wiring between battery and servo connector.