How to downgrade from Monterey 12.6.7 to 12.6.6 ?

App & System Services Core OS
OSX_rulez OP
Created May ’23
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Hello, I wanted to upgrade an iMac 5K late-2015 from Mojave to Monterey (external boot HD Seagate Exos), but I did a mistake (probably) and installed 12.6.7 and now the Mac doesn't start properly. It just boots and restarts constantly. I tried to reinstall macOS with internet recovery Monterey 12.6.6 but I got this error: "com.apple.buildinfo.preflight.error 21". If I want to reinstall starting with the internal HD already with 12.6.6 it says it can't downgrade the external volume.

How can I fix that error without erasing the volume?

Thank you!

Replies  1
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App Store Connect Engineer OP
Apple
May ’23

We appreciate your interest in participating in the forums! These forums are for questions about developing software and accessories for Apple platforms. Your question seems related to a consumer feature and is better suited for the Apple Support Communities

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How to downgrade from Monterey 12.6.7 to 12.6.6 ?
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