Removed shelves, icemaker and all panels from back of feezer to investigate. Turns out threaded fitting from water line going up back of fridge to water chute was not fully seated where they join. It is accessed from behind the fridge. Suspect it had been like that for 7 years but became worse recently. Put in new chute and icemaker since they last only 5 or so years just to be sure it was not contributing to problem. Did not replace water valve because it is functioning properly. Had thought that maybe its timer function was staying on too long and overflowing icemaker. Seven seconds was perfect.