3x3 upgrade got removed while updating the DW20 pack on FTB. My slider for size selection is stuck on 3x3, but I can't extract the module to further upgrade it (nor can I change back to 1x1).

I have the same issue.

Seems like the tag for the upgrade I have is three_by_three, but when I add it in a test world it's size_1 (and presumably five_by_five / size_2 respectively).

I was able to fix it by changing the tag in level.dat, removing the 3x3 module then re-adding.

You'll likely need to install a new one, sorry about that! Does it let you install a new 3x3?

Alternatively if you manually update the mod it may fix it.