Having intermittent trouble connecting to Android Auto to the Projection Icon on the 2017 Volt Display. Most of the time it connects just fine when I follow the sequence: power on Volt, start Android Auto, connect Volt USB cable to smart phone. However, if I use a different sequence Android Auto will not connect. Nothing I do can persuade the Volt to accept the Android Auto app. I have tried to power down the Volt, power off the smart phone, and restart the sequence with no luck. If I shut down the Volt for a few hours, the Android Auto will connect. Bluetooth connection to the Android phone works fine all the time.
Like you, I have experienced this less-than-reliable connection, via Android Auto. First with the LG G4 and now with the OnePlus 5. In the case of the OnePlus 5, have also experienced instances when the phone believes it was connected, but the Android Auto screen, on the Volt's infotainment center, was actually black.
I have also attempted to discipline myself into the same sequence you describe, curmugeon. And like you I have also found it sometimes necessary to disconnect the phone, even re-boot the phone, and power down the Volt.
I have found it is sometime useful to change the USB to the MTP connection type. That is, after the phone is connected to the Volt and Android Auto isn't behaving correctly, I swipe down on the phone's notification shade. I then tap the notification for the current USB connection type (probably it's the charging type). A dialog box is displayed and I select the radio button for the MTP protocol. When I then return to the Android Auto screen, on the Volt's infotainment center, I find I can sometimes successfully connect (and the USB connection type has returned to charging). If I do this, first, before I start rebooting everything, I sometimes find the connection can be made again.
All in all, I find almost a quarter of the time my car and phone fail to connect properly. That said, I agree the issue can sometimes be the USB cable itself. I should also note that I am using the same USB cable with the OnePlus that I originally purchased for use with the LG G4. I am now using an Aukey USB-to-USB-C converter. If I continue to experience especially the black screen, I'll probably see if I'm any more successful at connecting using a proper OnePlus Type C cable.
I should also point out that I have installed the little application called "Dock No-Op" (by Megagram). This allows me to more easily boot up, on the phone, Waze, after connecting the Android Auto. There are some instances when Android Auto pitches a fit about not being the default app, when the phone is "docked" to the Volt (Dock No-Op is made the default, to allow me to more easily access my phone's screen, while Android Auto is functioning). So, I admit I'm not making the Android Auto connection an easy one. But, on some drives, it's sure nice to have Google Maps on the Volt's infotainment center and Waze running, on the phone.