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I'm getting a lot of "Error 'Scsi error - Medium Error" or "Error 'OS error - Status_device_data_error'" in my event log:

The source file '/BDMV/STREAM/00294.m2ts' is corrupt or invalid at offset 27064320, attempting to work around
The source file '/BDMV/STREAM/00294.m2ts' is corrupt or invalid at offset 27064320, attempting to work around
AV sync issue in stream 1 at 0:00:02.880 with duration of 25.166ms : audio gap - 30.2 missing frame(s)
Error 'Scsi error - MEDIUM ERROR:L-EC UNCORRECTABLE ERROR' occurred while reading '/BDMV/STREAM/00294.m2ts' at offset '19709423616'
Error 'OS error - STATUS_DEVICE_DATA_ERROR' occurred while reading '\Device\CdRom0' at offset '19709423616'
Error 'OS error - STATUS_DEVICE_DATA_ERROR' occurred while reading '\Device\CdRom0' at offset '19709423616'
Error 'OS error - STATUS_DEVICE_DATA_ERROR' occurred while reading '\Device\CdRom0' at offset '19709423616'
Error 'Scsi error - MEDIUM ERROR:L-EC UNCORRECTABLE ERROR' occurred while reading '/BDMV/STREAM/00294.m2ts' at offset '19711979520'
Error 'Scsi error - MEDIUM ERROR:L-EC UNCORRECTABLE ERROR' occurred while reading '/BDMV/STREAM/00294.m2ts' at offset '19712311296'

Are these all bad discs? Or is my drive going bad?

For some reason your drive has gone off-line during the rip.

Possible causes: USB-powered external drives often run out of power if not plugged into a fully-powered hub. This happens when they start spinning faster than they have power available for. They come back on line after they reset.

SATA drives can decide to spend more time trying to read an error sector than the operating system is willing to wait. They're still working, but the OS says they've gone away.

The first is fixed by making sure the drive has sufficient power; the second usually by cleaning the disk.