Thank you! This was the exact same problem I was having, described here:
I did not realize I could name the directory as I wanted by using the "_FILENAME" parameter. I've mucked up a couple of directories by not being careful, and I was resigned to just having to clean up future mistakes, but this should mitigate almost all of those errors.
So in my case, I changed it from two actions:
Format Value:
"_FILENAME"
%artist% - %album% - $num(%track%,2) - %title%
Format Value:
"_DIRECTORY"
E:\Music\%albumartist%\'['%year%']' %album% '['$upper(%_extension%)']'\
to one action:
Format Value:
"_FILENAME"
E:\Music\%albumartist%\'['%year%']' %album% '['$upper(%_extension%)']'\%artist% - %album% - $num(%track%,2) - %title%