OK so the plot thickens as they say, combined by the technician at AMP's lack of product knowledge.
Reading the instructions for the kit part number provided, this kit is for PASSENGER SIDE ONLY. There are independent triggers for the slider and frong passenger door. The trigger wires are different colors that the purple/purple black that is standard for AMP STA controllers but good news they are identified in the documentation and the troubleshooting steps are the same (ground the trigger, see if the steps move, proceed based on results)
(instructions for the single sided kit PN provided by the OP)
https://static.thiecommerce.com/asse...67ea87e3f0.pdf
The reason for two controllers is you likely have two kits installed on your vehicle, one for the drivers side and one for the passenger side, each with their own controllers, which you already surmiesed. I can't find documentation for this kit so your guess is as good as mine to the OEM part numbers.
The standard dual-sided AMP step kit does use the purple trigger wires as previously described and includes a little module that sits out on the CAN and intercepts the door open signals. It also uses a single STA controller.
(Instructions for the dual side, single controller kit with CAN intercept module)
https://static.thiecommerce.com/asse...1c188a8f2d.pdf
Anyway long story short sounds like this is a real hodge-podge of parts, its fairly simple to troubleshoot but probably not going to be a black-and-white path considering the situation.
In theory a guy could un****ulate this if you can source the CAN module and wiring harness from the dual side kit, remove the relay and one controller, follow the wiring instructions for the dual side kit, and you would keep full functionality and remove failure points. I have heard AMP is tricky on spares and the instructions do not have part numbers in their instructions.