netCDF4 and ArcGIS

I am having issues using the netCDF4 module within my python script for one of my ArcGIS tools. The weird thing is, the tool runs fine the first time, but then when I run the tool a second time I am getting an error. The tool is no longer able to read from the netCDF file, and gives the error when I try to read the latitude values of the file. I then have to restart ArcGIS, and the tool then runs successfully once, but then if I run the tool again I get the same error and need to restart again. Does anyone have any idea what is going on here?

Thank you !