npm repository(proxy remote storage) error

Dear Sonatype Support Team,

We are currently experiencing a strange issue with our Nexus related to an npm repository.
Here’s the behavior we’re observing:

Repository > Proxy > Remote storage is set to profer external npm, but repository does not work as expected.

However, if we simply change URL and click “Save” — the error no longer appears and the repository begins to function correctly.
(even slightly, just add / and save, and delete / and save again)

Could you please advise on what might be causing this issue, and whether there is a recommended fix or workaround?

Thank you in advance for your assistance.

Best regards