That being said, I've outdone myself at breaking things while using this core in the process.1) Unless I set a max framerate cap, e.g. 50, I get blinking on the display right after booting up the rom with rewind state capture active. I do not get this issue when rewind capture is off. I only discovered this because I had left the framerate cap because Frogger has a similar kind of issue on my Samsung HDMI display.
2) Sometimes, but not always, I can get the display to blink on and off if I use fast forward. Once it starts it doesn't stop until I reload the whole core. Also, when it is in this state I can save state (which is hard to do because it's only visible 1/4 of the time and the other 3/4 of the time the display is black). When I reboot the core and reload the rom and restore state there's no issue. So whatever the issue is related to it is not the persisted game state itself but something else more low-level I think.
3) Rewind works. Kind of. But usually it glitches out horribly. The game state freezes and the audio also becomes garbled. Also many times when this happens the background glitches out as well with the foreground sprites frozen. I suspect that this is a kind of thing that I can save state and reproduce. In a way it reminds me a little of the Zelda Link to the Past audio glitches which were resulting from rewind state missing a few sound parameters. It would be strange if the sound timers were used by the game for background effects in Aria of Sorrow, but who knows?