What do you mean with "externally"? What tool did you use to check the SHA-1? Could you post the magnet with most but not everything after each "param=" Xed out?

For example

magnet:?xs=http:*****&xt=ABCDEFXXXXX

dn= shouldn't matter, drop that.

and also show the complete magnet with all values removed like this:

magnet:?xs=REMOVED&dn=REMOVED&xl=REMOVED&kt=REMOVE D

so that one can see the structure of the magnet. It might help if you contacted the developers directly because not seeing the magnet in full, is a pain in the rear but gnutellaforums are pedantically strict on these matters even if the magnet doesn't point to anything questionable ... oh well ...