gdalwarp leaves black boundary of cropped GeoTIFF with cutline

This is a new question based on a response on the thread white page border when converting geoPDF to geoTiff with gdal_translate

I am using gdalwarp as described to do a cutline of GeoTIFF images that have been rendered from geospatial PDFs. The neatline in the PDFs is not accurate but I can easily create UTM coordinates and adjust them accordingly to get the GeoTIFF image that I desire.

This is the CSV file. The coordinates are not square

id,WKT
1,"POLYGON ((410290.5552 4025996.01,410434.6684 4039895.26,421656.358 4039786.037,421530.3048 4025886.935,410290.5552 4025996.01))"

This is the command line:

gdalwarp original.tif original.crop.tif -cutline mycutline.csv -crop_to_cutline

The new image is square and the cropped image is canted inside as is expected. The problem is that the outer crop area is showing up as black. When I tile the image and display it on top of a map base layer, it aligns perfectly except that it has a black edge around it. If the edging was transparent then it would be fine, but the when tiled, it definitely retains the black color.

Here is a sample image
http://www.appalachianbiketrails.org/images/resized.tif

Here is the tile example
http://www.appalachianbiketrails.org/tiles/openlayers.html

I have tried adding the -dstalpha flag as mentioned in other posts and shown in the code snippet below, but that gives the error “Cannot compute bounding box of cutline.”

gdalwarp original.tif original.crop.tif -cutline mycutline.csv -crop_to_cutline -dstalpha

On a side note, I found that the direction of the coordinates in my CSV file determined whether the crop was inside or outside of the coordinates.