Recently, I found that if I do tactics puzzle on both the computer (web interface) and the phone (Lichess App), certain puzzles will repeat.
Let me explain in more detail:
1) First I do tactics puzzle on computer
2) Log off computer
3) When I use the Lichess phone app, I find that certain tactics are repeated from my previous session on the computer.
This is not a serious bug, but hopefully it can be fixed.
You can't post in the forums yet. Play some games!