Azure SCIM user provisioning cannot read extension field in mappings

Question

I have set up a provisioning of users from my customers AD. It works fine with all the basic mappings (displayName goes to displayname, streetAddress goes to addresss[Type='work'].streetAddress and so forth. All good.).

Customer has some fields in their on Premise AD that the have now added as extension values, but the app seems unable to access those.

The have now have this on specific users:

[extension_67bc2fb900fc4b39908324e3637f076a_postOfficeBox] = "Yes"
[extension_67bc2fb900fc4b39908324e3637f076a_postOfficeBox] = "No"
[extension_67bc2fb900fc4b39908324e3637f076a_postOfficeBox] = NULL

When I test this value in the expression builder it displays the correct value.

I am then trying to map the field to: addresses[Type='other'].postalCode

PROBLEM : When I run a provision on demand or it runs the scheduled provision the field is missing, and is not synchronized.

Attempt to resolve possible NULL values by mapping as expression:

Switch([extension_67bc2fb900fc4b39908324e3637f076a_postOfficeBox], "No", "Yes", "Yes")

Works fine in expression builder. Default is "No", and only those with "Yes" gets a "Yes".

Field is now always in the patch, but is always "No".

When I look at the result of the provision on demand it states that it has tried the expression:

Switch([undefined], "No", "Yes", "Yes")

It would seem that the context of the logged in admin-user in portal allows for reading the field in the expression builder, but that the context of the app that performs the actual provisioning does not know about the existence of that field.

I fail to find anywhere where I can see/investigate/correct this..... suggestions appreciated!