psilbhb hangs when psivideo exits

[bburan]

At the end of an experiment, psivideo stops and exits, but psiexperiment hangs and doesn't return to the launcher. We have to force quit and restart. Not a huge deal, but this prevents the launcher from saving the results of the last behavior session to celldb. This failure seems to be very reliable, so should be easy to replicate.

This occurs for runclass NFB. Not sure about NTD.