I finally had some time to get back to this issue and try some debugging based on the comments.
I reassigned the pins so that I could use the interrupt on pin 7 (interrupt 4):
//LCD display setup
LiquidCrystal_SR lcd(4, 5, 6);
// | |
// | \-- Clock Pin
// \---- Data/Enable Pin
#define encoderAI 7
#define encoderAQ 8
and I removed the second interrupt for simplicity:
attachInterrupt(4, handleEncoderA, CHANGE);
//attachInterrupt(0, handleEncoderB, CHANGE);
Yet the results I get for countA are erratic when I have lcd.print statements within my loop, and stable when I do not, and now there's no direct pin interference (that I'm aware of).
Any ideas?