Time is off when copying and pasting

I was up late one night making a beat. I was making a 8 bar loop because I had to put a slow beat in double time. I decided to do the drums in the first 4 bars and then copy and paste the rest of the drums in the remaining 4 bars. When doing so I noticed that the 1st bar (5th bar) the drumns were accurate but the others timing was completely off. I even tried to past each bar individually but I still was not succesful. Is they're a proper way of doing this? Any input on this subject would be most appreciated. Thank you very much.