Congrats on building the Cadets!
Weird that it does not work in non-genlocked mode, what are the symptoms? No output at all? If it does work when genlocked, it means the sync generator works properly, so maybe it’s an issue with the VCXO resting frequency, as described here:
https://community.lzxindustries.net/t/cadet-rgb-encoder-bmd-mini-analog-sdi/
When no external signal is present, the output of the PLL that controls the crystal should be around half VCC, so the crystal is at nominal frequency, then maybe the VCXO is a little out of spec and the nominal frequency is a bit off.
I would first try with another monitor, as maybe the one your using is a little picky if the sync signal frequency deviates from the standard. If does work with another monitor, you can try adding pull-up/pull-down resistor as shown in the topic mentioned previously to see if it helps. If it does not, maybe a replacing one of those resistors with a trimmer + small value resistor in serie so you can adjust the nominal frequency of the VCXO manually until the monitor picks up the signal. One drawback of adding pull-up/pull-down resistors is that it will result in a horizontal shift when in genlocked mode, so a solution is to use a switch to disconnect them from the circuit when needed.
Let us know how it goes 
(Loving that euroracked FFG in the bottom right of your case! Are the extra CV inputs to control the bitswap switches with an external signal? Really neat, would love to see how it looks once modulated!)