to force a resync of an bittorrent sync folder you can use the "touch" tool to update the timestamp
i'v used the http://ss64.com/ps/syntax-touch.html commandlet and saved it under "touch.ps1"
then startet powershell session
registered touch with
changed to directory where i want force the resync
issued list all files and piped it to touch
dir . -recurse -file | touch
you sould immediate see the resync of the missing files ...