Can you both confirmed that you did the quest in the following order?
"1 - Find a text in braille
2 - Find Mason Swanborough to read the document (he is in a hidden house inside a court, which is in the alley between the Whitechapel entrance near the Church and the cimetery)
3 - Search the 3 other texts
4 - Go back to Mason Swanborough
5 - Give him all the pages
6 - Return into the sewers (the same where one of the text in braille) and unlocked the door leading to the top in the laboratory
7 - Kill the Saint Paul's chemist
8 - Collect his diary
9 - Go back to Mason Swanborough and talk to him
10 - Choose between : give the treatment / keep the treatment
So, i thought i had all 4 braille notes because the quest said so. So i headed back to Mason and he told me to finding a lab, but the quest did not change. Since it did not make sence i decided to look it up online but did not find an answer, instead of restarting the game in hope that would clear bug. I thought why not just go to the places i found them and sure enough. I did miss one, even though the quest said i had all 4.
The one i missed was in the sewer next the a hideout (on the map it is southeast from cemetery)
I play on Xbox one.