On a setup where the file is updated on an OS X machine, and synced to 64-bit FreeBSD and Linux boxes. With version 1.2.73, I occasionally get an issue where a single file just refuses to update. The file keeps on being re-transmitted over and over. The receiving party shows the following error in the log; PIECE 0 FAILED HASH CHECK It's actually quite difficult to get rid of this error. So far the only thing that has worked for me is to move the file to ~/tmp, stop all clients, remove any remaing !sync and !syncOld files, start all clients, and move the file back into the sync folder.