DP 5.0.2 Correct way to build kernel and modules? nvgpu.ko errors!

Hello together,

I have followed this guide:

https://docs.nvidia.com/jetson/archives/r35.1/DeveloperGuide/text/SD/Kernel/KernelCustomization.html

I am using the manual sources.
Using the nvbuild.sh works. A kernel is compiled.
Instead of creating a kernel supplements tar as described in step 7 I install the modules as follows:

rm -rf $ROOT_DIR/usr/lib/modules/$KERNEL_VERSION/kernel
make -C $SOURCE_DIR/kernel/kernel-* INSTALL_MOD_STRIP=1 LOCALVERSION="-tegra" ARCH=arm64 O=$KERNEL_DIR modules_install INSTALL_MOD_PATH=$ROOT_DIR/usr

This all works perfectly fine. We added custom kernel modules and everything runs properly.
Now since we have noticed that a lot unneccesary stuff is included in the kernel config I for example disabled the “Network Device Support → Wireless LAN” option in the kernel. Everything else is kept the same.

As soon as I run the generated kernel and modules on the device I get the following warnings from nvgpu.ko:

[   10.174511] nvidia: loading out-of-tree module taints kernel.
[   10.177739] nvidia: module verification failed: signature and/or required key missing - tainting kernel
[   10.178623] nvidia: disagrees about version of symbol nvhost_get_default_device
[   10.178784] nvidia: Unknown symbol nvhost_get_default_device (err -22)
[   10.178974] nvidia: disagrees about version of symbol fget
[   10.179093] nvidia: Unknown symbol fget (err -22)
[   10.179252] nvidia: disagrees about version of symbol fd_install
[   10.179397] nvidia: Unknown symbol fd_install (err -22)
[   10.179674] nvidia: disagrees about version of symbol wake_up_process
[   10.179815] nvidia: Unknown symbol wake_up_process (err -22)
[   10.180092] nvidia: disagrees about version of symbol iterate_fd
[   10.180257] nvidia: Unknown symbol iterate_fd (err -22)
[   10.180563] nvidia: disagrees about version of symbol __close_fd
[   10.180745] nvidia: Unknown symbol __close_fd (err -22)
[   10.181399] nvidia: disagrees about version of symbol nvhost_syncpt_unit_interface_get_aperture
[   10.181644] nvidia: Unknown symbol nvhost_syncpt_unit_interface_get_aperture (err -22)

Is there anything special about the build of nvgpu.ko that it does not get informed about my kernel config changes?