To achieve this dupe all you need to do is connect item conduits to the sarcophagus and a chest and items will be inputted into the chest. Tested on 2 different sarcophagus's and both times a Dirty Scepter was put into the chest. By adding speed upgrades to the item conduits the flow rate of Dirty Scepter's that come out will increase. This was tested on a multiplayer server running version 2.4.0 of Divine Journey 2, Atum2 version 2.0.20, and Sponge Forge.

Here is an image of the dupe setup: https://imgur.com/xzYiA4i

Is this before or after the Pharaoh have been defeated?

It's before the Pharaoh has been defeated this has also been tested and confirmed to be a problem in singleplayer.

Could you try with this build in singleplayer? :)
https://jenkins.girafi.dk/job/Team%20Metallurgy%20Mods/job/Atum%202/job/Atum%202%201.16.5%20Jenkins/294/

Closing, as 1.12.2 is mostly unsupported now. If you can 100% confirm that this is an Atum issue, rather than an EnderIO issue, please open a new issue.