It would appear that the schedule I gave for milestones was a bit too enthusiastic.
As you know, LWB6 is a complete rewrite of the game. In a different language. And therefore, using different libraries, some of them chosen completely at “random” (that is, based purely on API cleanliness).
Two weeks ago I noticed that, despite the fact that everything I had actually worked, I was having major performance problems. This prompted a rewrite of 75% of the code I already had.