Okay thanks Fubar.
I'll extract and move your IXB mask_type9 file into the sensors.dat file of 'Extended Radar' mod, then remove the entire 'sensors.dat' file from your IXB skin. That should work great!
I am using your VII-C, IXB and XXI skins, so will forget about placing .tga files in the 'Texture' folder.
There's another sensors.dat file with the 'cablefix' mod (fixes cables on the VIIC I think), which also interferes when applied with JSGME. Sounds like I can do the same thing with this mod too.
This is something like my 10th campaign(?), and I don't remember ever using the IXB sub 'til now. The bridge-dial could have been like that from the very beginning.
I have a 100% stock (compressed) backup of SH3, and can check the bridge-dial from there.
Thanks again!