The problem is fixed and very easily. I am posting to describe the fix
because I found advice in this group which was correct but did not
specifically address this model.
The refrigerator is a GE Profile TCS18P bottom freezer with a drawer.
Ice formed on back and collected in the bottom of the inside cabinet.
Eventually enough collected such that water leaked out the sliding
door. As several posters pointed out the problem was with the drain.
The evaporator coils reside between the refigerator and freezer
cabinets. The drain line runs directly to the exterior on the back to a
trap concealed by an insulating cover. Removing seven sheet metal
screws allows one to disconnect the trap and clean it. Mine was full of
some mater that best remains in my memory and no one else's.
I hope this will encourage others to fix this problem themselves. The
owner's manual and GE web site were no help whatsoever though the
problem is so easily rectified.