When choosing Watch Replay, my units do nothing

[Thalatta]

I've tried to Watch Replay a couple of times after a game, and in both instances the same thing happened: my units do absolutely nothing and I lose the game.

But that's certainly not what happened 

[Gurken Khan]

Single player, you resumed from a save? The replays can't handle that. Supposedly one can merge the partial replays, but so far nobody was able & willing to tell me how. (And a botched frankenfile disabled the game for me until I deleted it with a file manager.)