@Pepe Today I refreshed my SDCARD with image from July of TOS 5.0.3 and TOS 3.11.17 to make sure BTFS filesystem is clear. I made sure to check it is clear by btrfs check --repair --force /dev/mmcblk0p2 and get completely no errors. Then I upgraded snapshot of TO 3.11.17 to TOS 3.11.19 without any problem. After that tried update of TOS 5.0.3 to TOS 5.1.0 with same error as reported before with same error results as happened on TOS 5.0.4. Sending diagnostics to tech support by email.
INFO:Queue removal of python3-hyperlink
INFO:Queue removal of luci-i18n-ahcp-en
INFO:Queue removal of luci-app-ahcp
INFO:Queue removal of ahcpd
Press return to continue, CTRL+C to abort
INFO:Downloading packages
ERROR:(https://repo.turris.cz/hbs/turris1x/packages/base/libuci_2019-09-01-415f9e48-3_powerpc_8540.ipk) Opening output file “/usr/share/updater/download/libuci-2019-09-01-415f9e48-3.ipk” failed: No file descriptors available
line not found
line not found
line not found
WARN:Crash report of stack trace dump failed.
DIE:
[string “updater”]:114: Error while registering for download: https://repo.turris.cz/hbs/turris1x/packages/base/libuci_2019-09-01-415f9e48-3_powerpc_8540.ipk: Unable to open output file for writing
Aborted