I have a Make Bumper two tiles from Fit Rear Bumper and configured to Only Import Locally and it doesn’t. So I’ve added a Mini Supply Stockpile in between both and configured to Only Import Locally and only rear bumpers and it has the same behaviour it doesn’t import.
One thing I’ve noticed on the Make Bumper is when you move the mouse over the inventory it shows the name of the item it’s there. Out of the 12 items, 10 are front bumpers and 2 it doesn’t appear anything.
If you need the saved game let me know.
I’ve noticed this bug as well. I saw on a previous post Cliffski mentioned this should be fixed in 1.53. What causes this is the rear bumpers take slighter less time to fit than the front which means the demand for rear bumpers is slightly higher.
When creating the bumpers locally, every time there is a spot available it will start a production cycle of 2 front and 2 rear. Since the rear bumpers get consumed slightly faster and because the bumper manufacturer will place the two front bumpers before the rear bumpers, you will find it get to the stage where you are stuck with front bumpers only. For example, when one slot is available, it will start a production cycle and once complete, it will place the front bumpers first which means the rear bumpers never got produced. Placing stockpiles only delays the problem.
You will find this happens with other parts like arches that follow the same rules. (Produces 2 front and 2 rear)
Hope this is explained well enough.