Suffering exactly the same problem trying to install 14.1.2.6 on Virtual Edition running 14.1.2.5.
Tried deleting and re-creating the volume, same problem. Checked and MD5 hash is fine, in fact i have been able to install a standalone test instance with 14.1.2.6 (from 14.1.2.5) without any issues.
Tried re-installing 14.1.2.2 which was on the volume orignally, and with that I now get the error "failed (Could not access license source; sda, 1 )"
*** Live install start at 2020/07/07 18:09:08 ***
info: Daemon-driven execution indicated by ENV variable.
info: Repository tm_install version/release is 2.12.0.3/6.0
info: System tm_install version/release is 2.12.0.6/4.0
info: Platform id is Z100
info: Basic disk format validation passed.
error: status 8192 returned by command: mount -oro /dev/vg-db-vda/set.1._usr /mnt/tm_install/30190.WXdfNO/usr 2>/dev/null
info: >++++ result:
info: mount: /dev/mapper/vg--db--vda-set.1._usr is already mounted or /mnt/tm_install/30190.WXdfNO/usr busy
info: /dev/mapper/vg--db--vda-set.1._usr is already mounted on /usr
info: /dev/mapper/vg--db--vda-set.1._usr is already mounted on /opt/.sdm/usr
info: /dev/mapper/vg--db--vda-set.1._usr is already mounted on /opt/.sdm/lib
info: /dev/mapper/vg--db--vda-set.1._usr is already mounted on /opt/.sdm/lib64
info: >----
error: status 8192 returned by command: umount /mnt/tm_install/30190.WXdfNO/shared
info: >++++ result:
info: umount: /mnt/tm_install/30190.WXdfNO/shared: not mounted
info: >----
Terminal error: Could not access license source; sda, 1
*** Live install end at 2020/07/07 18:09:09: failed (return code 2) ***