Ask HN: What are you having trouble with in machine learning projects?

Hi, Assuming you do it professionally, how do you go about your machine learning projects? What is your workflow? What tools do you use and why? How is your team organized? How do you collaborate and hand-off each piece of the puzzle? How do you handle data, develop your models, track experiments, deploy and manage your models, etc. I'd love to hear your thoughts. Disclosure: we're building a platform for our own needs for now, but I'm interested in how people who are more sophisticated and organized do it. Thank you,