Hello,
I created a 100x70mm PCB - SCH and layout using KiCad 7.0.1. All the checks - SCH ERC, PCB nets and DRC - had passed with resonable results (the DRC reported on few clearance violations where I connected two pads with a line to set a default connection - may optionally be disconnected and rewired for a;ternative configurations).
Then I generated the Gerber files according to the PCB manufacturer (PcbWay) instructions. However, the manufacturer claims that layers are merged. The attached picture shows the merged cupper layers.
Without knowing what you have done (which steps exactly) there are multiple possibilities:
false pcbway instructions (maybe they are referencing a different kicad version?)
you followed the instructions not exactly
kicad bug (very unlikely)
My guess: you did not read the description texts in the gerber output window.
See picture below, there are two different sections for the layer-checkboxes.
Most probably you will only want the left row, leaving all checkboxes on the right (“Plot on all layers”) unchecked.
Also I recommend to check the gerber output (for instance with the internal kicad gerber viewer) prior to sending the gerber to any board house.
