Hello @Alexander Diehm
This may be related to some cached information, drivers issue or even intermediary network hardware filtering. If the computers work in a different network without issues, you can discard a workstation related issue, however, a driver update would be convenient to ensure that is not related.
I would suggest to start looking into the SBS DC, in Event Viewer for specific Errors or Warnings related to DNS resolution or DHCP assignment. You can also use this on the workstations to gain a better understanding.
Additionally, you can test a new computer in this network: if the computer fails, it is a intermediate network issue (hardware such as switches, routers, firewalls) and if it works, it means that the issue is definitely on the SBS.
Hope this helps with your query,
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