diniboy

Hi, After a few hours of playing I experienced a huge TPS lag on my two player server. If I try to break a block, it appears again... The TPS is usually 0,48... And even the server stopping takes ages... However in the nether, or even farer from my house everything is okay. How can I debug what block/entity/mod causes this? My PC is strong enough (I gave it 2-10 GB of RAM) and my Java 8 is 64 bits. Thanks!