I consider it remarkable that such a circuit is still being built from conventional digital logic.
As far as i understand, such design is now understood as inflexible,
because it is hardwired.
Maybe it is a good exercise for students.
my question is, if the OP has designed the circuit freshly, or if it was found in a book etc.?
also it is unknown if it is the OP's own website.
when i look the schematic, there is some device which has a BCD or 4bit hex output.
I'd suggest to install a mechanical hex/BCD encoder, and test the circuit.
anyway it's a limited design, as far as i understand only one load can be selected at one point of time.