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Season 1 Disc 2 (episodes 4 and 5)
Season 4 Disc 3 (episodes 6, 7 and 8 )
Season 5 Disc 1 (episodes 1 and 2)

Don't know if the problems are being caused by bad discs or the software but I can't make mkvs or back up the discs.

With what you've provided, any suggestions would not even qualify as wild ass guesses.

Could you turn on debug logging (link in my signature for more information on that), and copy/paste some of the error messages into the body of a reply?

Log sent to support@makemkv.com

This one for Game of Thrones (GoT) Season 4 Disk 3 Episode 6. Similar logs for other episodes. Visually the discs are clean, wiped over with an eyeglass lens cleaning cloth even, and free of scratches, finger prints, bite marks, etc. I'm not ruling out a reader issue, or even a microscopic blemish on the disc surface, but it seems to have happened with three different GoT discs from three different seasons from when the discs were brand new until now, and I haven't had many (if any) issues with other BDs that are in good shape visually.

I rip to a solid state hard disc on a hex core i7 Windows 10 PC with 32 gigs of RAM, then move the successful files to a big "spinning rust" array, so I'm sure the hardware downstream of the reader (LG WH16NS40) isn't causing a bottleneck.

Can you post what error message you're seeing? I've ripped all seasons with no issues. Also, please read this: http://www.makemkv.com/forum2/viewtopic.php?f=8&t=15055

Typical Errors reported in the program window:

Error 'Scsi error - MEDIUM ERROR:L-EC UNCORRECTABLE ERROR' occurred while reading '/BDMV/STREAM/00045.m2ts' at offset '3574394880'
Error 'OS error - STATUS_DEVICE_DATA_ERROR' occurred while reading '\Device\CdRom0' at offset '3574394880'
[Repeats X times]
DEBUG: Code 3221225628 at 0*u53V?r+$wd$Pq.aI:121262969
Error 'Scsi error - MEDIUM ERROR:L-EC UNCORRECTABLE ERROR' occurred while reading '/BDMV/STREAM/00045.m2ts' at offset '3574394880'
[Repeats X times]
DEBUG: Code 100864261 at 0*u53V?r+$wd$Pq.aI:121262969
Error 'Scsi error - MEDIUM ERROR:L-EC UNCORRECTABLE ERROR' occurred while reading '/BDMV/STREAM/00045.m2ts' at offset '3574394880'
DEBUG: Code 0 at 8=h{tZTtt133Ig!gb;mX:121263291
DEBUG: Code 0 at zjJ4tTzD?zIb*hXiSG\):121262302
DEBUG: Code 0 at 8=h{tZTtt133Ig!gb;mX:213130812
DEBUG: Code 1745310 at 8=h{tZTtt133Ig!gb;mX:29393286
DEBUG: Code 0 at T:}L'Aj<w&w(~v+!IEKR(:29398967
DEBUG: Code 0 at T:}L'Aj<w&w(~v+!IEKR(:29398967
LIBMKV_TRACE: Exception: Error while reading input
Failed to save title 1 to file C:/Custard/New folder/GOT S4 D3/Game_Of_Thrones_Season_4_Disc_3_t01.mkv
Error 'Scsi error - MEDIUM ERROR:L-EC UNCORRECTABLE ERROR' occurred while reading '/BDMV/STREAM/00074.m2ts' at offset '6502281216'
Error 'OS error - STATUS_DEVICE_DATA_ERROR' occurred while reading '\Device\CdRom0' at offset '6502281216'
[Repeats X times]
DEBUG: Code 3221225628 at 0*u53V?r+$wd$Pq.aI:121262969
Error 'Scsi error - MEDIUM ERROR:L-EC UNCORRECTABLE ERROR' occurred while reading '/BDMV/STREAM/00074.m2ts' at offset '6502281216'
[Repeats X times]
DEBUG: Code 100864261 at 0*u53V?r+$wd$Pq.aI:121262969
Error 'Scsi error - MEDIUM ERROR:L-EC UNCORRECTABLE ERROR' occurred while reading '/BDMV/STREAM/00074.m2ts' at offset '6502281216'
DEBUG: Code 0 at 8=h{tZTtt133Ig!gb;mX:121263291
DEBUG: Code 0 at zjJ4tTzD?zIb*hXiSG\):121262302
DEBUG: Code 0 at 8=h{tZTtt133Ig!gb;mX:213130812
DEBUG: Code 3174942 at 8=h{tZTtt133Ig!gb;mX:29393286
DEBUG: Code 0 at T:}L'Aj<w&w(~v+!IEKR(:29398967
DEBUG: Code 0 at T:}L'Aj<w&w(~v+!IEKR(:29398967
DEBUG: Code 0 at T:}L'Aj<w&w(~v+!IEKR(:29398967
LIBMKV_TRACE: Exception: Error while reading input
Failed to save title 2 to file C:/Custard/New folder/GOT S4 D3/Game_Of_Thrones_Season_4_Disc_3_t02.mkv

Like I said, I'm not ruling out problems with the discs themselves or with the reader, but it seems odd to me that so many of the GoT discs have been prone to this problem.

And, can I borrow your discs?

My experience is that those errors are due to problematic discs, though it could be your drive as well. Follow all recommendations in the link I sent earlier (clean disc, adjust retry, etc.) then be prepared to replace the discs. Though it may seem surprising that you've had so many failures, it's really not as uncommon as you'd think...unfortunately...

Darren Heal wrote:And, can I borrow your discs?

I hope you won't be totally insulted when I kindly say "no".