The Samba-Bugzilla – Bug 6542
rsync: hlink.c:125: match_gnums: Assertion `gnum >= hlink_flist->ndx_start' failed.
Last modified: 2011-02-22 11:03:05 UTC
See attached file
Created attachment 4407 [details]
If you can still reproduce this error, try the latest git repo for 3.1.0 and pass rsync --debug=hlink5 so that it shows some hard-link debug info.
Since your command was lacking -o, this was most likely the corruption bug that was just recently fixed.