Okay I completely restarted Ferdinand's path. I made sure to hit all the necessary art points to not lengthen the romance more than necessary. I got to April 1st. Denis and Nat talked to me about being sad when I returned from 55, but when I tried to continue past the conversation it takes me to a new day. The only selectable option on the new day is the riverfront for painting, but the text says "Testing label: something seems to have gone wrong..."
Again, sorry if this is confusing. I think this time it progressed further before I reached an error, but I still wasn't able to get to the end of Ferdinand's path.