Problem with custom image and locale setup

[landorg]

Hello
I'm trying to use installimage to install a custom ubuntu 22.04 image.
During network setup I get this error:

[13:34:38] fatal: netplan generate stderr not empty:
[13:34:38] :   bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8)

The locale seems to be set correctly in the image (using ubuntu autonstall with locale: en_US.UTF-8)
If I manually chroot into the new OS and run the netplan generate command manually I don't see that output.

I worked around this for now with a custom installimage version where I commented out the return 1 in case of some stderr output and the installation works fine.

Any idea what could be causing this or how to prevent this?