Multiple servo switch on load issue

It might (very tentative might) help if you connect a resistor (say 4700 ohms) between each servo signal wire and GND to ensure the signal is steady in the interval while the Arduino is going through its reset routine.

I'm assuming from your lack of mentioning it that the Arduino power is quite separate from the servo power supply so that the Arduino is not affected by the fall to 2.7v.

...R