Here is a 2010 dated PDF of a recall on the 1200 series for the temp sensor.
https://www.thetford.com/wp-content/uploads/2015/03/Norcold-Recall-Notice_11_02_10.pdfI searched and searched and cannot find a recall on the N6XX series. I have one N611 now (2008 Thor trailer), and had another one in a 2007 Winnebago motor home and have never heard of a recall on them.
Charles
'03 Ram 2500 CTD, 5.9HO six speed, PacBrake Exh Brake, std cab, long bed, Leer top and 2008 Bigfoot 25B21RB.. previously (both gone) 2008 Thor/Dutchman Freedom Spirit 180 & 2007 Winnebago View 23H Motorhome.