uniform darkening but poor sharpness

The appointed neutral density filter was delivered promptly after ordering. After the Amazon packing opening there was the first surprise: the (slightly dusty) filter was in a plastic container without additional packing (usually such items in an additional glued or welded cellophane or plastic wrap tightly packed) in the Amazon envelope stuck. This plastic container has neither a label with product name, company name or logo, but only a sticker with a bar code.
Here once came to the suspicion that it was not here to Shipped in original packaging, but an article that another customer had already sent back.
But after the filter seemed otherwise undamaged, so I made a number of test shots.

First, the positive results:
Screwing and unscrewing the lens (Canon EF-S 18-135 IS STM) went without problems.
Then I will take a series of test shots by I (almost Full Frame) have photographed with different filter settings from minimum to maximum at different apertures and with 2 different focal lengths (90 mm and 135 mm), a sheet of white paper. My fear that the darkening is not uniform on the scene, has not been confirmed, the paper was in the pictures evenly gray, there was no discernible color cast. With this series of tests, however, I could not properly assess the sharpness, so I made a 2.Testserie. In addition I have made about 4 meters from the braided back of a garden chair photographed (first one shot without the filter, focal length 135 mm, aperture priority mode with Aperture 8, focused manually and then 5 images with different gray scale settings of the filter, the same then again with Aperture 11th

Which brings us to the negative and disappointing result:
According to the product description of the filter provides the best performance when used with lenses with focal lengths of less than 200 mm, 200 mm, the image quality may suffer somewhat.

When my test images were all (with the exception of the two images without a filter) so blurred that I classifies the filter as unusable.

That the filter is uniform darkening caused no color cast and with 35.99 is much cheaper than other filters with just a shade of gray, not comfort across the poor picture quality.
I'm going to the filter return and rate of this product from (it may already have a reason that other good Vario filter 120, - cost.