@zaldasan 

In my experience with MR600v2 + ISP FW, most of these blocks are cosmetic only (the underlying mechanism is intact).
If this is the case with nx510v, you have very good chance of unhiding these html elements . 

The best extension i found is a firefox (desktop) one called 'unhide nodes'  https://tinyurl.com/2xt9zr5f

To use it, start firefox, goto 192.168.1.1, goto the network page where these band option is missing etc.., click 'unhide nodes' button from FF toolbar, click on the page where the band select should be and it should become visible .

If you dont want to use FF extentions for some reason , You can also do it  but it can be more tricky to navigate / configure.
In Firefox goto 'view' > 'page style' > 'no style'

This will remove CSS and expose hidden elements .