Pro Tools 2019.10 enabled the setting of high frame rates in session setup.  Prior to a framerate being set in session setup, a default framerate value is also not established and subsequently instantiating the send/return plug-ins will cause Pro Tools to crash.    We are working closely with Avid to resolve this.

 

The workaround is either create a session from  the supplied template or to set the framerate to a standard framerate in session setup prior to instantiating the send/return plug-ins on aux tracks.