Some type of lag, maybe?
Android App Tacktics bug
I don't think it's lag. I didn't wait forever, but waiting didn't resolve it and if you press skip, it skips instantly, so the app didn't freeze. Also looking at the analysis board later when it happens only shows up until the move it happens although the tactic should be longer.
It is fairly rare however, I don't think it happened more than three times for me, although I usually am on the desktop version rather than the app
Weird. Next time it happens, can you please submit a bug report here on web providing time and date so we can actually check if its related to a malformed puzzle and I ll investigate from there.
My next guess would be connectivity but not likely because you don't see pass that move in analysis.
Ok, I'll try to remember it next time. I think when I checked on the web version, it worked just fine including the analysis.
I suspect that something with the move order gets messed up, so it thinks it's the opponents turn. I think that because sometimes when I fail several times and am out of ideas and click on hint, sometimes it plays back the opponent's last move instead of the hint move and then it's locked since it's the opponent's move. This happened just a while ago with this one https://www.chess.com/puzzles/problem/772178
Maybe I clicked too fast or doubletapped so it called the function again while it was in animation of the current move and thus "went a move back" so that it was still the other side's turn when it's done, but that's just a guess
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I can't really pinpoint what triggers it, but it happened several times. Sometimes after getting a puzzle wrong, it doesn't call the new buttons where you can repeat the last move or start over. Instead the menus remain from when you're doing the puzzle, except all the pieces are locked and the only option is to skip the puzzle completely.
It would also be nice to see the puzzle rating and par time and all the other stuff after completion.