Unable to upload image and being redirected to home page

Dear All,

Almost in many times, we insert/upload image(s) into our post, we got a blank page and the image was not inserted/uploaded. Every time we open the spam folder in comments menu or install new plug-in, it was redirected to the home page. We have been experiencing these issues since early this year. We have reinstalled the WordPress and performed version downgrading, but the problem persisted. Any idea or lesson learn that we can use to resolve these issues?

Many thanks,

Andreas