sylva-units-operator can't upgrade, old stuff in HelmRelease spec

My development environment is right now in the following situation:

🎯 Trigger reconciliation of units
Wait for sylva-units HelmRelease to be up-to-date...
sylvaunitsrelease.unitsoperator.sylva/sylva-units condition met
sylvaunitsrelease.unitsoperator.sylva/sylva-units condition met
Wait for sylva-units HelmRelease to be ready...
watching resources on namespace: sylva-system
 ✓ GitRepository/sylva-units-08cb6773 - Resource is ready
 ✓ HelmChart/sylva-system-sylva-units - Resource is ready
⠈⠁ HelmRelease/sylva-units - UpgradeFailed - Helm upgrade failed for release sylva-system/sylva-units with chart sylva-units@0.0.0-git+7082a7053069: values don't meet the specifications of the schema(s) in the following chart(s):sylva-units:- source_templates.sylva-core: Must validate "then" as "if" was valid- source_templates.sylva-core.spec: Must validate at least one schema (anyOf)- source_templates.sylva-core.spec.ref: Invalid type. Expected: object, given: null- source_templates.sylva-core: Must validate all the schemas (allOf)
Error: exiting as condition "reason" equals "UpgradeFailed" in unit HelmRelease/sylva-units, message: Helm upgrade failed for release sylva-system/sylva-units with chart sylva-units@0.0.0-git+7082a7053069: values don't meet the specifications of the schema(s) in the following chart(s):
sylva-units:
- source_templates.sylva-core: Must validate "then" as "if" was valid
- source_templates.sylva-core.spec: Must validate at least one schema (anyOf)
- source_templates.sylva-core.spec.ref: Invalid type. Expected: object, given: null
- source_templates.sylva-core: Must validate all the schemas (allOf)

indeed, I have:

$ k get hr sylva-units  -o yaml | yq .spec.values.source_templates
sylva-core:
  spec:
    ref: null
    url: https://gitlab.com/sylva-projects/sylva-core.git

looking closer (--show-managed-fields), this comes from kustomize-controller manager, which can only be explained that this field was set by the bootstrap cluster management-sylva-units which was setting this field

I would tend to think that the problem should occur on "1.5 to main" pipelines, but I can't see it occur.

In any case if I saw it, I think it could occur on any "old platform" (mine is > 1 year old).