Same issue encountered in
https://www.drupal.org/project/drupal/issues/2795965 →
but in the latest recommended version.
Getting this message though provided correct X-CSRF-token.
{
"message": "X-CSRF-Token request header is invalid"
}
Fixed
9.2
rest.module
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It's likely this issue predates Contrib.social: some issue and comment data are missing.