Video problems when using OBS virtual cam

I have a client with a setup for classes in their Gym that has a PTZ cam that is setup to use NDI because of the distance from the camera and the PC.  I am using OBS with the virtual camera plugin to support the NDI to the PTZ camera.  This works most of the time but occasionally when they try to start a new zoom session the video that is seen is static image of the end of the previous session.   I reboot of the pc seems to solve this but sometime they have multiple sessions with only a few minutes in between and a reboot causes delays.  Trying to find out why this is happening and how to prevent it from happening.  Another work around they have been using is to share their screen in zoom and pull up the OBS window and clink on the live view of the NDI camera.  This works  in a pinch but it is showing other parts of the screen they don't want or need to display.  This is being used for exercise classes so they only need the camera view.