Problem with interlaced mode and black frame insertion

[M-a-r-k]

Snes9x2010 (but not any of the other Snes9x cores) seems to have/cause a problem with black frame insertion when the emulated console outputs interlaced video. Not sure whether the problem is in this core or RetroArch but anyway...

I'm testing RetroArch Android on a phone with 120Hz screen with black frame insertion enabled. BFI works fine with the other Snes9x cores. But running a game that enables interlaced mode in Snes9x2010 (e.g. 240p Test Suite, there's an option at the main menu for that) causes the phone display to flicker a lot, as if alternate should-be-not-black frames are black too.

Also, the controller overlay flickers when that happens too. Is there something which is very CPU-heavy about interlaced mode in Snes9x2010 specifically?