[Phpbb] Forbidden error when editing posts

[khtcodpc]

Good Evening ~

Since a few days, I've noticed, by my users and myself. that everytime we try to edit a single post, an error appears:

The problem is that this error enables ourselves to edit our posts. There's something I can do to resolve this?

Thanks for the support ~

 

[khtcodpc]

I've been doing testings and it usually happens in posts with some internal links in it. I can post whatever i want, but if I try to edit it later, i begin to get the Forbidden error...