Hello Fabio,
You may wish log an issue with support to work through the scenario. I think we're stumbling over a language distinction which a remote session may be able to clear up.
Regarding your statement:
2 service types with service targets are attached to an incident but only one of them attaches their targets. I think SDM should attach the targets of both service types.
Note these parts of the documentation:
You can only assign a service target template once to a service type. Many different service targets can be linked to a service type.
During the ticket creation, a Service Type assigns one or more service targets to track each stage of the ticket resolution. Each time the ticket changes, the active service targets evaluate the condition.
So that is to say, you can attach multiple targets, but only through one template.
Then the targets are evaluated individually.
I think you're coming unstuck at this point "2 service types with service targets are attached ".
If that is really what you need, and can't be worked around by the above, you may need to log an Idea to request this feature. But check first by giving more information here on your example scenario, and someone may be able to suggest a way to get that business requirement met.
Thanks, Kyle_R.