Got strange issue on ppsspp 1.1.1 iOS

[trieu]

Hello,
I'm playing Patapon 2 using PPSSPP iOS version for months and everything works perfectly.
But yesterday when I was playing, I toggled the ppsspp menu at the top to pause the game, then resume and I realize that the game suddenly runs a little bit faster than normal. I have to press faster too to keep up the beat and after some beats, the game becomes slower and the sound is crackly, I feel like it is cpu over loading, after some beats it continues to run fast again, repeatedly...
Restarting the phone or reinstall ppsspp doesn't help.
What should I do now? Please help