Guess it depends on your definition of big problem. Still requires calibration, and seems like it's a lot of MCU to MCU variation from what I've seen so far.
Dr Jones described the effort as a substantial one, here: https://budgetlightforum.com/t/-/36651
He modeled the PID algorithm and tested it - it sounded like it took months and still has some issues with responsiveness on higher powered lights, plus effected by heating of the 7135's when in use.
Plus his driver cost is substantial compared to the cost of this light. Not a big problem? Well...