Unexpected voice stealing in single layer patch

[metasim]

I have the 8 voice Rev2, and just noticed when building up a 5 note (maj9) chord using program F1P1
("LosVangelis2041", which has a single layer), the root disappeared. Neither of the Split or Stack buttons is lit, which the manual implies is the way to know a program has a single layer. Looking at the (tiny) voice assignment status shown at the bottom of "Globals" editing confirms that Layer A cycles through voices 0-3, while Layer B shows a static "7".

Any idea what's going on here?

[metasim]

Update: just figured out that I had "MultiMode" enabled, which appears to reserve/split the voices evenly between the two channels, even if they aren't enabled as a part of a split. Turned it off and am able to play > 4 note chords.