Chroma key problems [Panasonic MX70]

[bravedog]

Chroma key aka green screen is something I've used in many contexts, but today I'm getting weird effects with the Panasonic MX70 mixer. This mixer has 3 chroma key settings and one can set the color to be keyed by activating a cursor which acts as a color picker and pressing enter when cursor is over the desired color. This seems to work, with different RGB numerical values entering the screens for key 1 2 and 3, and staying in memory.

Key controls include setting K level or specificity of range of the key color, and slice and slope controls to fine tune edges. These seem to work roughly as expected.
However, the 3 key settings seem to all do exactly or almost exactly the same thing. I created an image with RGB areas to color pick which set different apparently correct RGB values for the 3 keys. Key 1 seems to work correctly [Green] But when I switch from Key 1 to Key 2 or 3 [red, blue], I see zero difference in what is keyed out. What might I be doing wrong? I referred to the manual and some online videos without being helped.


Update 7/19 With more experimentation, I found the answer in my wrong assumptions. All 3 keys are always simultaneously active whenever Chroma is on, which is why nothing changes when switching from key 1 to 2 or 3; all that does is allow tweaking of the settings for that key.