How to fix REST API error?

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I get these error.

error:cURL error 28: Operation timed out after 10000 milliseconds with 0 bytes received (http_request_failed)
error:cURL error 28: Operation timed out after 10001 milliseconds with 0 bytes received (http_request_failed)

As a result of various investigations, I found that this error turns ON and OFF when this plugin changes to enable or disable.
And I tried to disable Collect User Statistics option. But it doesn’t fix.

https://wordpress.org/support/topic/rest-api-request-failed-and-loopback-request-to-your-site-failed/

How should I fix this?
I have bought PRO ver.