Process is opened like valid if the node coordinates are outside of sub-process and this sub-process element in bpmn file contains the node element (in xml file).
This should never happen, because it is not possible to operate with such a node.

Attached process brokenNodesInsideSubProcess.bpmn was modelled with all Events and Tasks inside Event sub-process.

• After importing process to business-central, these nodes are placed on the top-level canvas instead of event sub-process because of the wrong coordinates (see wrongSubProcessLevelNodesPlacement.png).

I found it by accident and currently I cannot reproduce how the process with invalid coordinates can be created, but a user should be prevented before it, because bpmn file, which was modelled in different editor, can be imported or the coordinates can be changed manually as well.