nunit-console leaves zombie processes in mono 3.12 vs proper behavior in prior versions (3.10)

There is a behavioral difference between mono 3.12 (latest beta) and 3.10 in that if I run the latest production nunit-console ( in a build script it runs the tests, but leaves behind TestAgency processes running at 100% cpu that never exit.

I suspect that there is a library change related to concurrent collections, processes, or threads, whereby these processes are left spinning.

If you are not able to reproduce can try to provide more info.