I seem to have found a way for it to work every time - I managed to repeat it in all my factories.
The glitch is extremely simple and will save you lots of time.
- Wait for your product to reach maximum
- Buy supplies. Once that's done, you have to wait 10 minutes.
- Once the supplies arrive, sell your product as fast as you can.
This will cause the supplies to never descend, essentially making them infinite. All you have to do now is wait.
If you have any questions you're more than welcome to.E
EDIT: FIxed as of 1.37. Was good while it lasted...