I have:
SCC 150/35, firmware 1.63
Venus OS 3.3 on a Raspberry pi
VE.Direct USB cable (genuine) between the two.
In VRM, if I do a scan for firmware updates, and then immediately go to the dashboard after it is finished, the SCC has disappeared! However, if I wait up to my refresh interval, it reappears in VRM.
I know of at least one other pi user that this happens to, and a Cerbo user where it does not happen.
I suspect the firmware scan interrupts/resets/interferes with the USB driver or VE.Direct protocol.
I know VenusOS on a pi is not "supported" but it may be good feedback to Victron engineers that this is occurring. I can reliably reproduce this at every firmware scan.