okay i went on youtube to find a lets play and to see if i am insane and i am not
the one i found is the second but in the video it shown has the first so wtf

edit: i found a more recent lets play and it also shows has the second so wtf

Well, a lot had changed since the full release of the game. Especially names and numbers of many milestones, tablets etc. My guess is that you are missing this milestone here;
https://www.youtube.com/watch?v=Liyg0UDSm0k

It´s very well hidden in a secret kind of a cave behind these pillars here;
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=1948977173
Use the teleporter to get behind the pillars.