Unexpected error when adding routing steps

Hello everybody.

I have this problem:
I have created a route.

Then when trying to add a newly created assemblyitem (All types of assemblyitems break) to any operation sequence (routingcomponent/(component per operation)) and calling objrecord.save ends up returning "Unexpected error". I know that it is that certain assemblyitem, because I tried removing it and everything worked.
Now, I have already in the script created routes and assigned routingcomponents to at least four different routes with the same functions.

When I add all "component per operation" -info through the user interface in the route everything works.

To clarify:
In the code I have called objRecord.commitLine({ sublistId: 'routingcomponent' }). This still works. When I call objRecord.save({ enableSourcing: true, ignoreMandatoryFields: false }) it throws an Unexpected Error without any information on what broke.