We recently are having instabilities in the designer plugin which makes user tasks, mail tasks, .. disappear after reopening a workflow.
In the attached workflow you'll see a 'mailtask2' that should be visible on the bottom lane but it is'nt. If you look in the xml the mailtask2 is correctly assigned to the lane but it looks like some graphical information is incorrect
Other users are also complaining about user tasks disappearing. I made sure they are were working on 5.15 which is the latest version but the issue seems to be in that version too.
Eclipse Standard/SDK, Version: Kepler Service Release 2, Build id: 20140224-0627