Hi! This might be a bug, or you might have run into some kind of size limit. If you go to C:\Users\{username}\AppData\LocalLow\sokpop\sokworlds, what size is the biggest file there?
I found a problem on the server that might have caused this. Please try again - if it doesn't work, could you send me the local.sok file on bugs@sokpop.co? Then I can have a closer look to see if it's a server issue or a client issue. Thanks!