intermittant water on floor, pan is mostly dry

Very occassionally, without rhyme, reason or pattern we find water on the floor in front of our side by side Kenmore Coldspot 106.56936600. Looking undernearth, there is no visible wet path of water through the dust. The tray under the freezer is almost but not quite dry, you can tell there has been water in it but it definitely is not the source of the problem. It appears to come from about the middle of the refrigerator side of the unit centered front to back and side to side. No evidence of leaking at the supply lines to the icemaker or the valve. No water or ice buildup inside either compartment. Happens every month or 2 sometimes, then every week sometimes and has been going on ever since we bought it used. (Wonder why it was for sale?)
Where should I look, what should I take off or check? I followed the advice form this source on an ice maker problem years ago and it worked great.
Thanks, BW

(Unit Manufactured in 2006)