I'd really like an answer to this question that was posted here: Extract by mask arcpy script error
I too am trying to iterate through sub directories and extractbymask my study area from bands of Landsat data.
I'm getting the same weird output of erroneous NoData values: 0 and -37268.
Not sure why the arcpy version of this code won't work since the GUI tool works fine in arc, but I need to use arcpy to run this process on about 2000 rasters.
Thanks for your help and let me know if I can provide anymore info. I'm using 10.4.1