@BLK ISF thanks, good to hear your experience has been smooth. I've been in contact with GROM and we're slowly ironing out these issues (at least I hope so, so far just a lot of sending logs/firmware back and forth).
Are you able to tell me how you're getting the EQ up? From what I understand, the EQ settings for FM and say AUX, CD or USB are different. I say this because I have EQ settings set for FM but when I went to AUX, it's at default. In any case, I can't access the VLine (USB setting for me) EQ as that immediately enters VLine interface. How do you bring up the EQ then?
As for the buzzing sound, it comes on even just on acc on, no need to start the engine. Very likely its the amp as @_ISF said, as it went away briefly whilst doing a VLine firmware update and the unit rebooted then the buzzing resumed. However I have noticed that it no longer always comes on...suggests a wiring problem perhaps? I did the wiring myself, but I'm no stranger to wiring up car audio and have triple-checked my work when these issues started showing.
Edit: I've had the VLine few months now, but now only actively trying to solve the issues as I'm driving the car more now. It could be the amp is faulty, I've read a few threads around the internet of Lexus Mark Levinson amp buzzing. I've arranged with Lexus of Perth to inspect the issue and hopefully replace under warranty if it's faulty (still have about 2.5 years warranty remaining). Finger's crossed they won't say the VLine voids the warranty cover!