I found out, by accident, that if you change the layer order, by using those up and down arrows, the OSC information doesn't move along. Which makes me sending an OSC command to the wrong layers. For example Opacity of Layer to layer2 makes the opacity of layer3 changing.
Without even testing with a OSC application, you can see it when you press on OSC Mapping. First change layer order. If this is a feature, I have a hard time figuring out why.
edit: ok, figured out a users case for this.. the good old relative vs absolute values problem...