I am using VDSL2 internet and Deco works fine.

However when I saw that my ISP can send up to 70 Mb/s to my modem and not just 50 Mb/s that I had been using, I requested the higher speed tariff.  ISP processed it and said that the change was successful.

But the internet speed through my Deco X20-DSL was still about maximal 48 Mb/s (both via UTP and wifi on all devices) as it was before the ISP upped the tariff.

I saw that "Current Rate (up/down):" in advanced section of the web UI increased in the down section from about 60000 where it was to 76000 kb/s with the tariff change, but the internet connection speed was still the same. Tried to look for firmware updates (none found), tried to reboot the device from the app, tried to reconnect DSL line, nothing helped, everything ran just 48 Mb/s even when they gave me 100 Mb/s tariff with real speeds of 70+ Mb/s.

After contacting the ISP support as the last resort, they have verified that from their side there are no issues and suggested I factory reset the modem. I did that and after that it started to give speeds around 70 Mb/s - this was excpeted before.

I know I have just described an issue and a solution, but I also know that there will be an option to even faster VDSL speeds in my area next year and when that happens I do not want to factory reset again and lose all the settings. 

Is this behaviour a feature or a bug that can be addressed in an update? Or it can be solved in some way I did not know about? Seems weird that one needs to factory reset to get a speed update.