I would be
very surprised if any of this is MC's responsibility.
You need two things...
1. An understanding as to how your library became 'broken'
and
2. An understanding of how to achieve your goal in the future without 'breaking' your library.
You're MC library database is founded upon where on your hard drives the files are saved at the time you import them.
If you subsequently move those files to somewhere else, then start MC, it will have absolutely no way of knowing where you have moved the files to, therefore, the library will be 'broken'. Loads of red 'x's everywhere and 'make sure the path is right' error messages.
This is why, in your previous thread, JimH said:
If you move them inside MC, that won't happen.
MC has many powerful tools, the simplest being the good old fashioned 'drag and drop', that allow you to move files around without breaking your library. When these operations are performed internally, MC keeps the library up-to-date with the new file locations and nothing gets broken.
If things have gotten broken, they are more often than not fixable by simply telling MC where you moved the files to, which is what Matt was getting at when he said:
You can also use Find & Replace on the filename field to fix it. (i.e. replace C:\ with D:\)
Try the suggestion park has given you, but make very, very certain that you are using either a clone, or that you make a backup of your library before experimenting.
Look under "File > Library > Backup Library" and "File > Library > Library Manager" for more help on this.
If you are unsure about any of the above, then take a deep breath, and state, calmly and precisely, exactly how you moved your files, and where you moved them from/to, and if you're willing to learn, you will get the help you need to fix things without loss of library data, including playlists.
-marko.