New Mac mini M4 keeps ejecting SanDisk G-Drive with no notification

I've looked over the forums and can't find anything exactly like my issue, so hoping someone has an idea of what to do...

Just upgraded to a new SanDisk Professional G-Drive 18 TB ((Exact model here) to store media for a Plex media server setup. Had it connected to my 2020 M1 Mac mini (8 GB RAM/256 GB SSD) along with an older 10 TB G-Drive (Exact model here). Both are externally powered. I didn't have any issues whatsoever.

After a couple weeks I decided to upgrade to a 2024 M4 Mac mini (16 GB RAM/215 SSD), and suddenly issues started cropping up.

The older 10 TB G-Drive still works fine, but the newer 18 TB drive keeps ejecting itself - not even a 'Disk not ejected properly' notification. After anywhere from 5 to 20 minutes, it just disappears. I tried jiggling the cable in the port, thinking maybe the connection was loose, but to no effect. I have to unplug the drive each time and plug it back in.

I have tried swapping the USB-C cables (the cable included with the hard drive, plus two different Mophie cables, and the cable from the older drive), and tried each of them in each of the three USB-C ports, but no change at all: the drive keeps ejecting.

I also fiddled with the power settings, as many have recommended for USB-powered drives (preventing automatic sleeping; NOT putting hard disk to sleep when possible). Again, no change.

I generally access the Mac mini via screen sharing with my MacBook Pro, but the issue still crops up when connected to a monitor.

I've had a similar set up for almost five years without issue: a Mac mini used as a media server, always on, with external HDs always mounted. It's worth mentioning I previously had a USB-powered LaCie drive used for the same purpose and never had a problem. I'd be inclined to think it's the SanDisk drive at fault, but it worked flawlessly with the M1 mini.

Whew! So... any thoughts?