curl <https://media.nngroup.com/static/css/31c8ad03ff66.css>

returns the file compressed unasked. to uncompress this is necessary:

curl <https://media.nngroup.com/static/css/31c8ad03ff66.css> --compress

if this command is run:

httrack -v <https://media.nngroup.com/static/css/31c8ad03ff66.css>

it returns this error:
Mirror launched on Sat, 31 Dec 2016 16:37:53 by HTTrack Website Copier/3.48-21
[XR&CO'2014]
mirroring <https://media.nngroup.com/static/css/31c8ad03ff66.css> with the
wizard help..
16:37:53	Warning: 	Cache: damaged cache, trying to repair
16:37:53	Warning: 	Cache: 0 bytes successfully recovered in 0 entries
16:37:53	Warning: 	Cache: error trying to open the cache
16:37:54ps://medWarning: p.com/sRetry after error -5
(error:00000001:lib(0):func(0):reason(1)) at link
<https://media.nngroup.com/static/css/31c8ad03ff66.css> (from primary/primary)
16:37:54ps://medWarning: p.com/sRetry after error -5
(error:00000001:lib(0):func(0):reason(1)) at link
<https://media.nngroup.com/static/css/31c8ad03ff66.css> (from primary/primary)
16:37:54ps://medError: o"error:00000001:lib(0):func(0):reason(1)" (-5) after 2
retries at link <https://media.nngroup.com/static/css/31c8ad03ff66.css> (from
primary/primary)
16:37:54	Warning: 	No data seems to have been transferred during this session!
: restoring previous one!
Done.
Thanks for using HTTrack!

is this a bug or do i need a argument to tell httrack to uncompress?