Same here, brand new M1 iMac, two LaCie's ejecting every couple of minutes. I can't work, I can't back up, it's a nightmare. It seems to be worse when they're both plugged in, and the 4TB connected via USB-c does it more often than the old 1TB which is connected through a USB (which is in a hub going into the USB-C). Sort it out Apple, totally unacceptable.