Mackie surfaces use a special peak meter type that returns the maximum
peak for all channels in the strip. The issue was that the implementation
of this meter did not follow the falloff the other peak meters. If a real
peak meter and a combined peak meter were displayed on the surface at the
same time the missing falloff was obvious.
Don't calculate the combined meter during run. Instead calculate it only
when needed based on the already existing individual peak meters.
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