DB Lock

When I use applyAML, sometimes it will cause DB Lock.

What conditions will cause this cause?

By the way, I have the error message.

When I applyAML =><AML><Item type='Activity' action='EvaluateActivity'><Activity>109890D287C24699A1EA639B921F3E18</Activity><ActivityAssignment>698758D37ACA41FDA7A23A3B412868C1</ActivityAssignment><Paths><Path id='3DD97DD4DAE948608796D353E71AF337'><![CDATA['Approve']]></Path></Paths><DelegateTo></DelegateTo><Tasks></Tasks><Variables></Variables><Authentication mode=''></Authentication><Comments></Comments><Complete>1</Complete></Item></AML>

=> System.Xml.XmlException: An error occurred while parsing EntityName. Line 4, position 203.