Hoping to provide a useful (yet not "official" hint)... Consider to reboot your router before upgrade the firmware.

@Joseph-TP Thanks for the useful informations. :) For the release notes, may the community have a link to read them? Most of the users do not use support page, however... a lot of other users might...

Hi @Joseph-TP, thanks for your answer. I'm sorry being late for the follow-up, however I hope this experience could help also other persons. For several reason, I did not took the "contact support"...

https://community.tp-link.com/en/home/forum/topic/716222 Exactly as the linked, every several days (15-18) the device resets itself, after 8-10 months of correct operation. Tried also to update to...