Have you contacted Alpine directly regarding this issue?

 

Many USB decks will lock up when you get over 1 or 2 gb. Read the manual as many brands have limitations. Also your file structure, non FAT formatting and dead files will mess it up. Many noname brand drives have residual files built in as well. You should reformat it occasionally to clear the stuff off and put only playable music files on it. jpegs etc confuse it.

 

I'm also having the same issue and have documented it here:

tinyurl.com/CDE103BT

 

Sounds like a firmware issue.