Illuminati walls

I was playing a game recently, a scenario about the Italian Wars. As always, in the first turn I walled whatever I wanted to wall. I don't remember my exact walls and didn't ss them at that moment, but in thestart of t2 they looked like this:

Walls coloured red are wallfucked ones, blue circles and lines are my enemy's wall. Accidental wallfuck is a normal thing and often happens in scenario so I just sent the common "no abuse" message and carried on. On turn 2 I attacked the northern 2 units of his wall from Florence and the southern one from Rome. At the start of t3, however, this happened:

At first I thought it was just abuse, but njab guaranteed me it wasn't. In the end, eventhough I actually had a 4-layer wall, njab attacked Rome the next turn. How did this happen?

Hax.