I am currently reshaping the evaluation a bit and while doing that I noticed a very subtle bug. Instead of using the piece table for black bishops I used the table for black knights. This resulted in black thinking fiancetto was a bad thing since the knights get a penalty for standing on the G7/B7 squares, and also a smaller penalty for the D7/E7 squares (which are quite natural for the bishops).
I had been thinking about adding even more incentive for developing the bishops since it looked like they were rarely developed properly. This bug was probably the problem though.