Found why Regulation Mode was once again broken. Looks like the router applies default wireless values every time the radio is restarted, which caused reg_mode to be once again set to off. I had added that code after fixing the original issue so that European AC68U users would still be able to use DFS.
Now I enforce "d" only if we have a DFS-capable router and if it was set to "off".
Now I enforce "d" only if we have a DFS-capable router and if it was set to "off".