Adding a 12v fan blowing to circulate air should help, easy to install, on your drain, more then likely the tin coils get a little ice on them, when you shut the unit off they will defrost causing more water to be added to the drain pan. Is the only thing I can think of. The fan will also help stopping the frost on the fin plate. Also you mention that it different then your home refer, that is because they are. At home you have defrost cycles in your trailer the only way that happens is by shutting it off. Best I can think of...
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