I have created a minimal example to demonstrate the problem:
I have a collapsed subprocess inside an expanded subprocess. The collapsed subprocess contains only a single User Task and the necessary start/end events.
When I now save and close the process model and reopen it, the collapsed subprocess is displayed emtpy upon inspection, with its content floating on the top-level process:
Interesting sidenote: When I move to collapsed subprocess, the content belonging to it that is now displayed on the top level is also moved.
I used the latest flowable/flowable-ui container without any further configuration for the purposes of this test. Is anyone able to confirm this issue? Should I open an issue on GitHub?