Tablet Collection Glitch

[JackFrost]

I wanted to get the english percussion flintlocks so I went and collected all the absetergo tablets and got the final fainting with the church and X on it, so I wont back into the animus and went to the church but the X wouldnt appear and it wont allow me to dig where the pistols should be, I know where they are because I've gotten them before in a previous save but I like this save much better, so I left the animus and checked it out and for some reason it said I was still missing tablet 18 (I had already gotten tablet 18 in that save and I did still have the final painting in my inventory) so when I went to tablet 18's location, it wasnt there (as I said, I had already gotten it) but it still said I was missing it and it still wont let me get the flintlocks, am I screwed or is there a way to fix this?

[Pedrof]

I've encountered the same bug on the PS4 version. Very frustrating.