Hmmm, I tried playing with the settings but I could't get any wiser. Some work somewhat, some not at all.

Channel down works sometimes but channel up never works. Same is for keypad, numbers 0,2,5,8 are working, other numbers: No reaction.

I noticed that 50-60K frequency somewhat works everything else not so I think it's safe to say that it 56K is the right frequency.
I did notice however that duty cycle 5 gives me better results but still not the results I would like to get or to make this keyset useful.This is only my experience after quick testing, so maybe 36K could give me anyhing with other buttons and duty cycle. I don't know but I am trying to rule out variables but I should do some more thorough testing for this. This are only my experiences after a quick debug session.