Use TNT near dragon head will crash.
Server log:
[11:31:57] [Server thread/INFO]: Username lost connection: TranslatableComponent{key='disconnect.genericReason', args=[Internal Exception: java.io.IOException: Broken pipe], siblings=[], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null, insertion=null}}
Duplicate of MC-86138. If you have not, please search before reporting issues to see if your issue has been reported already.