KICAD IPC API only partly changes a footprint side when changing layer

Description

When using Kicad IPC API (through kicad-python), it is impossible to properly change the face for a component. When modifying the value of footprint.layer, only a part of the footprint is swapped.

Steps to reproduce

  1. Create a test schematic + board with two resistors. Use pcbnew to put R2 on the bottom layer.
  2. Run the following script, that is expected to put R1 on the bottom side
from kipy import KiCad

board = KiCad().get_board()
footprints = board.get_footprints()

for f in footprints:
    print(f.reference_field.text.value,f.layer)
# This shows 3 for TOP and 34 for BOT

footprints[0].layer=34
board.update_items(footprints)
  1. In the PCB editor, it looks as if nothing happened:
    image

... but in the info pane, the layer is set as B.Cu !
image

And in the 3D view, we have the copper&silk on top side:
image

But the 3D part on the bottom:
image

KiCad Version 

Application: KiCad PCB Editor x64 on x64

Version: 9.0.4, release build

Libraries:
	wxWidgets 3.2.8
	FreeType 2.13.3
	HarfBuzz 10.2.0
	FontConfig 2.15.0

Platform: Windows 11 (build 26100), 64-bit edition, 64 bit, Little endian, wxMSW
OpenGL: Intel, Intel(R) Iris(R) Xe Graphics, 4.6.0 - Build 32.0.101.6647

	wxWidgets: 3.2.8 (wchar_t,wx containers)
	Boost: 1.88.0
	OCC: 7.9.1
	Curl: 8.13.0-DEV
	ngspice: 44
	Compiler: Visual C++ 1942 without C++ ABI
	KICAD_IPC_API=ON

Locale: 
	Lang: en_GB
	Enc: UTF-8
	Num: 1,234.5
	Encoded кΩ丈: D0BACEA9E4B888 (sys), D0BACEA9E4B888 (utf8)
Edited by Ph Ma