When you import process from ARIS with nested swimlanes, you have to perform any action on the canvas to be able to save changes (swimlane migration to the top level of the process).
Without this "resaving" you won't be able to build&deploy the process. Error will be shown.
[KBase: defaultKieBase]: unable to parse xml : Exception class org.xml.sax.SAXParseException : <lane> may not be nested