Welcome to the forum! 
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Downgrading packages is not officially supported. Doing so can and will put you in an unsupported upgrade state.
We still have the NVIDIA 550.90.07 packages in the Manjaro stable branch. You apparently are using either the testing or unstable branch. Switch back to stable for now.
Using the installer directly is not supported and will cause conflicts with the official repo packages.
I’ve unmarked the reply as the solution.