After upgrading to Retrospect 10.0.0, I found that previous backups and copy operations would not work on my QNAP NAS using AFP shares. Some folders could not be opened by Retrospect. I tracked this down to a problem with .DS_Store files being renamed. It seems they may cause problems with the new Instant Scan feature. This proved to be a difficult problem to solve, but I believe I found the cause. I detailed this problem and a solution in this post on my web site:
I'm also going to bring this to the attention of Retrospect support.