Yeah I set it to 1 square mm, or whatever the lowest was. That's what I initially thought the problem was.
I only have 1 top and bottom layer set, concentric because it looks better on the mallet.
It seems to be treating the inside surfaces as top and bottom layers too, which if it acts like you're saying, it's giving it the concentric treatment (as shown in the photo, not the bridging treatment). I would have thought bridging would override it, but it seems like it doesn't.
I put the same model into Slic3r and it handles it perfectly. I triggered a filament change on my prusa just before it hit the bridge, dropped the weight in, and carried on. That was with the external layers set as concentric so it looked pretty
I'll keep fiddling!