Initially for one of the inner corners I had selected 2/3 edges for filleting. This caused fillet to bug out and some of vertices be position in completely wrong position far from where they should be resulting in visibly broken self intersection geometry in the are of that corner. Once I selected all 3 edges as asked in the drawing for exercise fillet was fine. But I don't see why it should have failed if the intention was to create model with 2/3 corner edges filleted. In other parts of model corners with such fillets worked fine.
Second problem was once I changed the angles and dimensions from phase 1 to phase 2. (I slightly cheated by not handling the bottom part properly but that's more of my failure read the drawing). After changing angle and dimensions fillets broke, and I had to reselect which edges are supposed to have them. (The topological naming problem). Which is slightly weird because the topology of model shouldn't have changed from those dimensions changes, but maybe there was a slight change in how boss intersects with bend, thus changing topology. In which case having to redo fillets is annoying, but slightly more understandable.
Third issue was that in the second phase it failed to solve fillets when radius was greater than 1.1mm (drawing asks for 2mm). Not sure why would it fail. I would understand if I asked something crazy like 10mm which would result in some degenerate geometry. But with 2mm it should still be sufficiently far from where it causes weird intersections. Again my best guess is the area with inner corner at the base of boss. There is short edge where outer cylinder of boss connects to bent corner instead of flat part.