Since it’s an instant webhook trigger, it is also possible that multiple instances of the scenario is being called close enough that they run together, which means that your sleep modules aren’t good enough.
You might need to try turning on “Sequential processing” in your scenario settings on top of 2s Sleep modules before each Shopify module in your scenario.
Hope this helps! Let me know if there are any further questions or issues.
— @samliew
P.S.: Investing some effort into the Make Academy will save you lots of time and frustration using Make.