1. Put down a machine that can accept modules.
2. Put modules of one type into the machine.
3. Make a blueprint of it.
4. Pick up the machine and modules.
5. Remove modules from your inventory, putting them in a chest.
6. Place blueprint.
At this point, the machine is expecting modules which you do not have.
7. Put DIFFERENT modules in the machine.
For an example of why you might do this, consider that the blueprint may have Speed Module 3's it expects but you only have Speed Module 1's on hand. So you put these in the machine instead.
8. Make a NEW blueprint of the machine with its new modules.
At this point, you have made a blueprint of a machine with BOTH the new and the original modules in it. This is an impossible situation to build. In my example, I ended up with a situation like this in my new blueprint.
You can see that this miner expects three Speed 1's and also three Speed 3's.
