Launchpad: MIDI mapping mode buttons -> LED weirdness

[robbmasters]

I'd like to turn certain LED feedback on and off when entering different Launchpad modes.

"Easy", I thought, "I'll just map the MIDI signal from the mode buttons to slots containing clips that do what I need."

And it works. Sort of.

But there's a snag. While doing this does seems to make the LED feedback for the grid behave as I'd like, it messes up the LED feedback for the mode buttons. For example, when I change mode, the old mode LED starts flashing, instead of going out. And the LED for the new mode starts flashing after a moment too. Also colours seems unpredictable (usually amber, but occasionally yellow).

Does anyone understand why? What can I do to achieve the desired result without messing up my mode LEDs?

Thanks.