Voltage regulator for AA battery pack
Have you tried an oscilloscope on the battery, motor, and IC power points?  It may be that your regulator cant quite keep up with a AA battery.  Those things can put out lots of AMPS under intermittent load.  The system may be experiencing a voltage drop when the motor tries to engage.  Electric motors at 0 RPM draw a huge intermittent load, known as the starting load, or starting current.  That is why in motor applications, like your refrigerator, fuses are slow blow, and breakers are delay type.  The simple fix, add a big capacitor to the output of the power supply.  The bigger the better (within reason).