We just upgraded to 2.7 and are experiencing something similar. When a job is first created, it has a parent of 0, but once we change something on the Descriptive Information tab and click Apply, it changes to -1. For the parents getting wiped out and replaced with -1, what we've seen is that it's fine when we first set up the job. We can make multiple separate changes to Descriptive Info, click Apply each time, and it's all good. But If we close the job (just the interface), open and make additional changes, then the parent disappears.
I do hope this will be fixed; we use parent jobs in our work as well.
Thanks, Lisa