If you ever bought direct downloads from them make sure to check that your files are error-free, especially if your downloads were slow.
Today I noticed that half of the files in four free albums by "クロネコラウンジ" did not decode properly. I redownloaded them all and one of the new files was still broken, but another attempt got me a good version. It was the only file that took about two minutes to get (today's first attempt), compared to several seconds for the rest, which suggests that under heavy load the file-serving part of their webmonkey code hiccups and starts sending you wrong file parts. Looking at the broken files in hexeditor you would notice content starts repeating in some random place (the starting position of the first part that gets repeated is aligned at 1 MiB boundary).