Code: [22:02:27] [Server thread/CRITICAL]: InvalidArgumentException: "NBT encoded length must be < 32768, got 65643 bytes" (EXCEPTION) in "src/pocketmine/network/mcpe/NetworkBinaryStream" at line 114 How to fix?.
That is not nearly enough information. When does this happen? Do you have a plugin causing it? What version of PocketMine are you using? What effect does the error have on your server?
This exception is thrown because of a entity clear all entities on your server Or on NetworkBinaryStream.php remove if($nbtLen > 32767){ in line 124
I guess it's caused by a player using a skin of 128x128 pixel. Some plugin may try to save it using a StringTag, which cannot hold this length of bytes. Are you using any plugin handling player skins, maybe for NPCs?
Go into your players folder and delete the .dat file for this player. He has an item in his inventory that has a too-large NBT tag.