Bob,
I mean if the label are so close together, we'll suppress some of them; but here is not the case definitely.
There is a property "SuppressPartialLabels" on the text style that defines whether suppress some label which rendered across two tiles. Or else some of the labels maybe cut for some reason.
Here is the code how to disable "SuppressPartialLabels":
Layer.ZoomLevelSet.ZoomLevel12.DefaultTextStyle.SuppressPartialLabels = false;
Also, I'm not sure what's your code like; I recommend rendering labels in dynamic overlay, and the label won't be cutoff. The key code is attached here:
renderMap.LoadLayers(Map1.StaticOverlay.Layers, Map1.DynamicOverlay.Layers);
If you have any questions please let me know.
Thanks,
Howard