Post content gone after more tag

OK, I noticed some thing very weird happened to my wordpress blog.

My post content after the <!–more–> tag are totally gone and the <!–more–> shows some empty link like https://www.myblog.com/my-post/#more-618.

When I edit it in WordPress editor all the contents after the more tag are gone, and <!–more–> tag also gone but shows up some html link instead.

For example, check this link:

https://www.blogiseverything.com/interesting/the-church-of-bones/

the more tag has become https://www.blogiseverything.com/interesting/the-church-of-bones/#more-588

and the content below are gone.