Are easements being ignored by the future neighbor?

Good morning.

The following situation:

We received a plot of land next to my parents from them and built on it quite some time ago.
Next to us is a larger hillside plot, which my mother and aunt sold last year.
In the course of the sale, my parents consulted a lawyer who helped draft the purchase contract.

The procedure was such that a 3m wide strip with its own plot number was created between our property and the hillside property, which is intended to serve as an access road for the development of the hillside property. At the end of this dead-end road is then my parents' property.

An easement granting pedestrian/vehicular access and a right of way for utilities was registered on the access road in favor of my parents and us.
Furthermore, a building prohibition easement was registered, which states that a 3m wide strip on the hillside property parallel to the access road must not be built on, especially where a boundary building would otherwise be permitted. (No boundary buildings are to be allowed at all)
This was to ensure that the buyer would not encroach too closely on all of us.

Yesterday, I received a letter from the building authority stating that the building permit for 3 single-family homes has been granted (3 single-family homes are basically fine with us).
In the site plan, I then noticed that the builder not only plans to build carports on the 3m strip on the hillside property but also planned a carport for the last house at the end of the access road.
This would stand directly on our boundary, instead of 6m away (3m access road + 3m strip building prohibition).
This is much more problematic for my parents, as they would not be able to use the access road with their pedestrian/vehicle easement to get to their property. Although their property is basically still accessible via their own access road from another street, that is beside the point.

In a phone call with the caseworker, I was informed that it is not the responsibility of the building regulation office to check compliance with land register entries. Their task is only to check whether any easement exists if such is necessary for the planned construction project. So if a builder needs to access via a private property, it is checked whether this is secured by an easement.

Although I am somewhat surprised by the fact that this is not checked by the building authority, we now have to consider how to proceed.
Of course, a conversation with the buyer is initially planned by my parents, but at the same time the lawyer will be contacted again so that he can review the situation.

How should one generally proceed if the conversation with the buyer leads to no understanding?

He signed the contract and should adhere to it.
Without wanting to accuse the buyer of anything, it is very hard for me to believe that this happened out of ignorance... ;)

I would be very grateful for any advice.

Best regards

So according to my own experience in another matter, there is only one thing to say: clarify this directly with the buyers or their planners. And if that doesn't work, then you already have the lawyer.

And forget about the building authority: they almost never help in such matters – unfortunately, you have to take action yourself.

The following situation:

Federal state?
Site plan?

It was arranged that a 3-meter-wide strip with its own cadastral number was created between our property and the hillside property, which is to serve as an access road for the development of the hillside property.

And was that sold together with the hillside property to the same buyer?

An easement for pedestrian/vehicular right of way and right of way for lines was registered on the access road for my parents and us.

Wording?
Is there a reference to a site plan?

In addition, a building prohibition was registered by easement.

In whose favor?
Wording?

In a phone call with the caseworker, I was informed that it is not the task of the building regulatory office to check compliance with land register entries.

That is correct. The examination covers compliance with public law regulations, not private law agreements. Therefore, the building permit is also granted without prejudice to the rights of third parties.

How should one generally proceed if the conversation with the buyer leads to no insight?

You can only assert or sue for your rights once they have been violated. If the buyer considers himself to be in the right, you or your lawyer can only take action if he actually violates your agreements secured in the land register. As soon as construction activities begin that suggest the implementation of the building permit, your lawyer should send an unambiguous letter.

which federal state?

I would file an objection prophylactically.
You can still withdraw it if necessary.

Basically, the building regulations office initially behaved correctly. I would try to have a conversation with the builder (a company?). It is possible that the planner simply neglected to check the existing easements.

Please show a site plan of the overall situation as IS and SHOULD BE. Thank you!