As I was about to finish the inspection, I notices there was a crack on the rear baffle supporting the oil cooler. This problem is known and I had tried to anticipate it by installing a steel brace (see here). It seems it was not enough.

The crack is the thin vertical line near the nutplate on the right.

The part is off the engine. The crack is on the smaller side on the right. Now, on to the repair.

The part is now repaired, I riveted a reinforcing angle.