hi, ive been hosting a server for a few weeks now, and just this morning there has been a huge problem. the server has had huge amounts of lag.. and when i say huge amounts i mean, freezes for upto 30 secs and then plays normal for half a second, then repeats continuously. the server is giving me with message every 30 secs or so " [WARNING] Can't keep up! Did the system time change, or is the server overloaded?". i have tried a lot of things such as: deleting all beta server files and re downloading and ect. i have also tried downloading custom maps and replacing the "world" with the custom one. the server is exactly the same settings as before, just different "world". this works perfectly. no lag, nothing. then i swap back and use my original "world" file and the problem starts all over agian. this immediately makes me think that there is something wrong with one of or some of the files in my original "world" folder. can someone please help me as my friends and i have been working on this server for over 4 weeks now and i do not want to start over.
i have left a link to download my original "world" folder if you would like it to assist me.

file : <link removed by admin>

thank you, your help is much appreciated.