Weird variations with 8-bit subtration circuit

[KoryTheKind]

https://steamuserimages-a.akamaihd.net/ugc/2015978842871368568/43A31C8D59CA19CD8942852905AC6A3C8D115E67/?imw=5000&imh=5000&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false

The correct value is "24"

I don't understand how one out of four of these subtraction circuits is computing different values. Help me understand?

[MegaIng]

For the bottom two, you have the wrong wire connected, since the second from the top messes up the wires going down the left.

The first calculates left - right (since the right wire is negated) and the second calculates right - left (since the left wire is negated).

[Stuffe]

unlike with addition, order matters for subtraction!