2019.6 Switching Hardware on startup to Source Nexus B

[SteveGarman]

I've been running 2019.6.0 for several months without a hitch on 10.13.6,
but now somedays when I turn the system on and start ProTools, it opens a session and when I hit play, no sound. I check setup>Hardware and see that Source Nexus B is there instead of HD I/O #1. I can restart but nothing changes. I open setup again and look at "Playback Engine" and see that HDX is a choice so I choose it. PT says it has to close and restart for that selection to take effect. i do that and then in setup Hardware I see HD I/O #1 is selected and all is well. But when it said Source Nexus B, I looked at Audio Midi Setup and HD I/O #1 was not even a choice so I had to restart and then choose my "Playback Engine' as HDX, then in Hzardware I would finally see HD I/O #1.



Why is it slipping back to Source Nexous B sometimes. It seems like it only does this on the startup of the day, but when you've got a client in there it's really embarrassing. Any ideas on what might be wrong? I have
an HDX card, HD I/O 8 x 8 hardware and HD Sync.