Hi,
Thanks for interesting question (and congrats on a nice RailClone style!).
One solution to this is to avoid using the Marker input on the generator. As you've pointed out, this divides the spline into additional segments and causes the Evenly counter to reset. Internally, it is similar to adding a Corner segment. Instead, I would wire the oven to the Default input via another Selector operator. Set the Mode to X Marker ID. You can then add a marker just before the desired X Evenly division and set the ID value to choose an oven. The only downside of this approach is that you will also have to add another marker to set the Default segment back to standard cupboard fronts. This can also be handy though if you wanted a number of different cupboard fronts in a row, you can use markers in this way instead of using Material IDs.
An amended version of your file is attached.
I hope that helps.
Paul