PSP Go no input in some games

[Las-pen]

I have PSP Go running on 6.61 PRO. Most games work perfectly, but in some games button presses won't register. The game starts and goes on, showing logos and finally main menu, but no matter what button (Arrows, L, R, Start, Select, X, O, /\, []) I press, it doesn't do anything, so the game is unplayable. However Home button still works, and I can quit the game, and control volume and brightness.
Doesn't matter whether the game was installed on Memory Stick or Internal Memory.
Games where this happens include: Patapon 2, 3rd Birthday, Monster Hunter Portable 3rd (English patched), Ace Combat Joint Assault (downloaded from PSN), and one of the Tenchu games (Shadow Assassins maybe). All from PAL region (except MHP3rd) , if that has anything to do with it. Unlikely since all my games are PAL. Isos work fine on my other PSP (1000) and on both of my Vitas.
Has anyone experienced anything like this with their PSP Go and what would be the cause for this?

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[Las-pen]

Okay, so I remembered that "doesn't matter if it's installed to Internal Storage or Memory Stick" part wrong. I tried all installing all games to the Memory Stick and they worked.
The next question is, why they won't work when installed to Internal Storage?

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[fate6]

Okay, so I remembered that "doesn't matter if it's installed to Internal Storage or Memory Stick" part wrong. I tried all installing all games to the Memory Stick and they worked.
The next question is, why they won't work when installed to Internal Storage?

Not all games support ef0 for some reason so it can cause weird issues from time to time.