@David_Kirk I will reply to myself then.
I have fixed this by swapping the mains powered USB HD, with a USB-powered 4Tb Toshiba portable HD. Smaller drive (physically), but now uses the USB power from the Pi. The Pi wakes it up as normal, and it works as it should.

@David_Kirk I will reply to myself then.
I have fixed this by swapping the mains powered USB HD, with a USB-powered 4Tb Toshiba portable HD. Smaller drive (physically), but now uses the USB power from the Pi. The Pi wakes it up as normal, and it works as it should.

Hi, I am only just getting into Recalbox, after being used to Retropie for a few years.
I have a Raspberry Pi 5 8Gb, 128Gb SDCard, and a USB 4Tb Hard Drive that is in it's own enclosure, and powered by it's own PSU. I am using the Pi in my own custom arcade bartop machine, with a zero delay encoder + 2x cheap zippy joysticks, and 8x buttons for each player. Everything works as intended, I have the latest version of Recalbox, and all my roms are on the 4Tb external USB HD.
Here is my issue. If I run any emulator, then leave that running, say MAME running Pac-Man (as an example), and I just want that running in the background, after about 10 minutes the external HD powers down and goes into sleep mode. Now, if I go back to the Pi, and decide to run something else, as soon as I quit MAME, or any emulator, the Pi will wake the USB HD up, and give me the following error in the pic.

I have set sharewait to 90, to give the Pi plenty of time to wake the drive - it can take a good 30 seconds just to spin up, and start accessing. If I follow the advice in the above pic, then Recalbox relaunches, but doesn't remount the USB HD, I have no roms, and my Joysticks are disconnected, and I am prompted to remap all the Joystick's buttons, and directions.
Sadly, I lack the Linux skills to attempt to fix this. So, if anyone has any ideas, I would be most grateful. Many thanks.