Again... if you post Arduino output pin voltages ..may be i can help you solve?..
I don't think most of these readings will be much help. For example the signal driving LCD Enable pin is typically low most of the time. There is a very short pulse whenever information is transferred to or from the LCD module. This will read '0' on most voltmeters.
The voltages on pins 2, and 3 with respect to 1 and 15 with respect to 16 are the only DC voltages present. These will be correctly interpreted by a voltmeter and might be of help.
try to add delay between the refresh rate of lcd.
The LCD does not have to be, and should not be, refreshed.
Don