Difficulties with publishing a rft with a python raster function from Pro to ArcGIS server 10.9.1

Hey!

We're unable to add our rft.xml file with a python raster function. We are referencing this path in the rft file:

[Install]\Server\framework\runtime\ArcGIS\Resources\Raster\Functions\Custom\subfolder\OurRasterFunction.py

Everything seems to work fine in pro where we can update the parameters we want to update and add the rft in our mosaic processing template.
But when we try and publish an image service with the rft file it throws an error telling us the template is invalid.
From the server logs:

Method failed.HRESULT = 0x80043010 : This is a FACILITY_ITF error that is specific to the interface that returned this error. See the documentation of the interface that returned this error for information about this HRESULT.

We were able to publish from arcmap 10.8.1, but then we dont get the capability of changing the parameter in the image service. Its stuck to the default value and we need to be able to deliver this to a customer that uses Pro.

It seems this is a compatibility issue between arcgis server 10.9.1 and the latest pro version when it comes to the template xml structure.
Do we have to upgrade to arcgis server 11 to make this work? Or is it any workaround that dont require to use Arcmap?

I can't share too much information as this is some sensitive data im working with. But i can answer any questions about the setup.