Hi there,
just wanted to share my experience: I wanted to update my TOS, but was stuck on 5.1.79. Trying to apply 5.1.123 was failing (with "failed to update") and OTA updates did not show up any available updates.
Thanks to Mike from support, I downloaded and installed 5.1.103 (-> viewtopic.php?t=5447&sid=1bd3da11a4e6f6 ... b19aa614ed) and was able to apply 5.1.123 onto it after that.
[SOLVED] F4-423 stuck on 5.1.79
Re: [SOLVED] F4-423 stuck on 5.1.79
Oh, and forgot to mention: I did have enough space, so that was not the reason.