Towers in end game are getting bugged

Just had two tower close to each other. After clearing the first one and opening the 3 slots i set up my 3 tablets. I went for the second tower which was 1 space away from the previous one cleared again to open the 3 spaces but after the tower was completed i couldt insert any tablets on it instead i am able to put again 3 tables in the first tower. When i do so message appears saying it was already used.