frozen sata ssd xubuntu 16.04 was solved under xubuntu 14.04.5

see expired question
https://answers.launchpad.net/ubuntu/+question/403839

SSD frozen once again

kernel.log
In the past the changing BIOS setting Storage Config from P/ATA emulation to AHCI cured the freezing.
Now after an upgrade the freezing is back.

In this example, after starting Firefox
dmesg
[ 130.824072] ata3.00: exception Emask 0x0 SAct 0x7fffffff SErr 0x0 action 0x6 frozen
[ 130.824086] ata3.00: failed command: READ FPDMA QUEUED
[ 130.824099] ata3.00: cmd 60/08:00:e0:5e:40/00:00:01:00:00/40 tag 0 ncq 4096 in
                        res 40/00:fe:00:00:00/00:00:00:00:00/40 Emask 0x4 (timeout)
[ 130.824105] ata3.00: status: { DRDY }
[ 130.824110] ata3.00: failed command: READ FPDMA QUEUED
[ 130.824121] ata3.00: cmd 60/08:08:e8:5e:40/00:00:01:00:00/40 tag 1 ncq 4096 in
                        res 40/00:01:00:00:00/00:00:00:00:00/40 Emask 0x4 (timeout)
[ 130.824128] ata3.00: status: { DRDY }
[ 130.824133] ata3.00: failed command: READ FPDMA QUEUED
[ 130.824143] ata3.00: cmd 60/08:10:f0:5e:40/00:00:01:00:00/40 tag 2 ncq 4096 in
                        res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
[ 130.824149] ata3.00: status: { DRDY }
[ 130.824154] ata3.00: failed command: READ FPDMA QUEUED
[ 130.824164] ata3.00: cmd 60/08:18:f8:5e:40/00:00:01:00:00/40 tag 3 ncq 4096 in
                        res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
[ 130.824170] ata3.00: status: { DRDY }
[ 130.824175] ata3.00: failed command: READ FPDMA QUEUED
[ 130.824185] ata3.00: cmd 60/08:20:00:5f:40/00:00:01:00:00/40 tag 4 ncq 4096 in
                        res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
[ 130.824191] ata3.00: status: { DRDY }
[ 130.824196] ata3.00: failed command: READ FPDMA QUEUED
[ 130.824206] ata3.00: cmd 60/08:28:30:5e:40/00:00:01:00:00/40 tag 5 ncq 4096 in
                        res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)

...
[ 2479.389046] ata3: EH complete
[ 2545.896056] ata3.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
[ 2545.896069] ata3.00: failed command: FLUSH CACHE
[ 2545.896082] ata3.00: cmd e7/00:00:00:00:00/00:00:00:00:00/a0 tag 19
                        res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
[ 2545.896089] ata3.00: status: { DRDY }
[ 2545.896097] ata3: hard resetting link
[ 2546.388056] ata3: SATA link up 1.5 Gbps (SStatus 113 SControl 310)
[ 2546.397016] ata3.00: configured for UDMA/33
[ 2546.397023] ata3.00: retrying FLUSH 0xe7 Emask 0x4
[ 2546.397570] ata3.00: device reported invalid CHS sector 0
[ 2546.397584] ata3: EH complete

Is a program say Firefox attempting to access sector 0
device reported invalid CHS sector 0
?
blk_update_request: I/O error, dev sda, sector 20995808
blk_update_request: I/O error, dev sda, sector 20995816

The SSD has been fully checked and cables replaced and connected to different SATA ports.
I've slowed the HyperTransport speed down to 600Mhz, sill getting errors.
CPu is not overclocked.
RAM fully tested & passed