then the wiring should be adapted!
I would like to better understand how the connections are made, the cables with lamps alixpress should be cut leaving 20cm of cable to insert the connector 4B0971992 as in the picture:

then you need to bring one cable for each seat that is connected to the positive and negative pin of bcm and the other side of the cable must be connected to the connector 893971632 as pictured:

One last thing, how you have connected the cable to the positive and the negative side of the bcm?