One field which is causing me problems is the [Name] field.
My usual workflow is to import and tag music and videos with my work pc, then I rename and move the files into the htpc using the "Rename, Move & Copy Files" window of MC. The two pc's are linked together via network cable. A second copy of MC in the htpc monitors a few directories and auto-imports all new files.
When MC imports an mkv it takes the name of the video from within the file if it has the tag (or from the file name if no tag is found).
When I modify the name, a sidecar file is saved with the new name into the <Field Name="Name"> tag.
Then I move the files into the htpc. After a while, the other MC imports the file. When I check what was imported I find that MC imported again the [name] tag from the file, not from the sidecar. I can try and force it, using the "Update Library (from tags)" command, but it doesn't work. The "Name" field into the sidecar however is still the one modified by me.
If the video doesn't have a title in its tags, MC reads the one from the sidecar.