Hi @Marc ,
1, Agree with Gideoney-4397, this can be a useful approach. Besides, there are something we need to confirm. Have you removed all the roles apart from Component Server and Site System before restart the SMS_SITE_COMPONENT_MANAGER service. I found an article, is this same as your situation?
The link for your reference:
Error while removing the Component Server role (prajwaldesai.com)
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2, Furthermore, in the following thread, many people provided some different methods to solve this problem. The link for your reference:
Deleting a site system that no longer exists (microsoft.com)
Looking forward to your feedback.
Best regards,
Cherry
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