2002 Eurovan Sliding Door Latch Problem - Low Ambient Temperature

I have a 2002 VW Eurovan. For the last two winter seasons, when the temperature drops closer to freezing, the door will not adequately latch. There are recommendations from owners on the web offering white lithium grease and lock thaw applications on everything… I had tried the litium but not lock thaw… anyone have the same problem and possible remedy? New latch?? What part of the mechanism should be replaced?