I have a very simple model, an air loop with an "OS:AirLoopHVAC:OutdoorAirSystem", an "OS:Coil:Heating:Electric", an "OS:SetpointManager:Scheduled", an "OS:Humidifier:Steam:Electric", an "OS:SetpointManager:Multizone:Humidity:Minimum", an "OS:Coil:Cooling:DX:SingleSpeed", an "OS:SetpointManager:Scheduled", an "OS:Air:Terminal:SingleDuct:ConstantVolume:NoReheat", a Thermal Zone with no equipment attached, and an "OS:Fan:ConstantVolume", like it is shown in the figure below.

This simple model is used to test the "OS:Coil:Cooling:DX:SingleSpeed" behavior, to check if the coefficients we calculated for the various curves of the coil model are correct. The preheat and the humidifier before the DX coil are needed to mimic the conditions of the external air since the weather file is used to reproduce the conditions of the exhaust air. This was needed because the real machine is working with the exhaust air as working fluid instead of using the outdoor air. In practice condenser and evaporator works with inverted temperatures. However, when I print the nodes minimum humidity conditions before and after the humidifier, I find this:

Does anyone have any clue about what is happening? FYI, in the weather file, the %RH is set at 30% (I used elements to edit it)

edit: added some informations