Slightly different, but just talked with a family member who custom-ordered a car trailer for a race car. They paid the deposit and dealer kept them informed of the progress of the order/build and requested the balance. Family member refused until delivery. After many months and may updates from the dealer than the trailer was just about done, would be shipped next week, etc., family member contacted the builder directly to find out they had his order, but had not started it because the dealer owed them for a number of trailers that had already been delivered.
Long story short, the dealer was ripping people off. Fortunately (if you can say that), family member is "only" out 2K. Builder told family member he had talked with about 10 other people in the same boat including a number who had paid the full amount. Clearly law enforcement is involved at this point and the family member may get his 2K back at some point, but it won't be soon.
Never pay in full for a big ticket item until you can inspect it and take delivery.