There are two quite distinct problems.

(1) There is a new bug that stops a download at 100%, retains the source and does not complete the handshake to initiate file verification and saving. The solution is to kill the download and to restart the download from the original hit in the search list. Once your machine attempts to reconnect to the host, it checks in the metadata file to see what is missing and realises that it has all it needs. For the benefit of the world I repeat my standard advice that you must keep the original hit lists until every download is complete.

(2) If you have the message "Cannot move to library" this suggests that you may have a corruption in the file. Again, you must kill the download and restart from the original source. However, this is not a guaranteed cure. If there really is a substantial corruption, nothing will save you and you will have to start again.