Post wp-admin/admin-ajax.php 403

The cache is causing the “Post wp-admin/admin-ajax.php 403” issue! However, the issue is gone if the cache is fully purged but it will happen again next day!

And I using the following expression in Cache Rules, it is also working well.
(http.request.full_uri contains "https://example.com/" and not http.request.uri.path contains "/wp-admin" and not http.request.uri.path contains "/wp-includes" and not http.request.uri.path contains "/wp-content")

Does anyone know how to fix the issue?

Does anyone know how to identify which file that shouldn’t be cached?