To change it to straight, right click :CC2EXPLODE: and pick the Smooth to Straight command to use on your poly. The process is also reversible with the straight to smooth option.

(Keep in mind that it will be easier to notice the difference inside CC3+ than on the exported image)

[When you convert the coastline to straight, you may notice a weird spike near the top left. This is caused by you going back and forth when placing the nodes, causing the lines to pass over each other and create a really sharp angle. I noticed it earlier, but the smooth polygon kind of hides it much more effectively than a straight one, so you may wish to go in and remove the offending node with :CC2DELNODE:. The node is located in the middle of the "cross" where the line spikes, not at the edge of the spike.]

I talked to the developer, and it seems it is the complexity of the coastlines that is causing the problems. It's only 5000+ nodes, but it is a smooth polygon, which increases the rendering complexity of the entity considerably, to the point where it is causing an issue if too much of it is rendered in one go.

One workaround is to do as you did, reducing the size of the bands, creating more passes, but less complexity for each pass. You could also turn the coastline into a straight polygon instead of a smooth one, as this will reduce the complexity considerably, but this may or may not change the appearance on the final map (Well, it does change the appearance, it is more if the difference is really large enough to notice or not, you can't zoom into an exported image as far as you can the CC3+ map itself anyway.) Note that you also have a landmass poly below the coastline, which is just as detailed.

It means you have selected the entity to trace at the wrong point. The trace will always go through the point on the entity where you selected it.

(Note that it might go the wrong way around untill you have moved the mouse enough from your starting point to pass the selection point)

The basic tools (from the right hand buttons) doesn't support advanced features like trace. This is available when using drawing tools (:CC2DRAWTOOLS:)

Joe is right about the resolution mode here.

What happens here is that CC3+ keeps each image in four different resolutions, so it only shows the resolution needed based on your zoom level for faster operation.

However, those affected trees of yours are not the same size as the rest of the trees, they're about 10% smaller. This means that when you zoom out, they switch over to lower resolution versions a bit earlier than the others, and if you hit just the right spot when zooming out, those trees have switched over to the lower resolution version, while the others have not.

You can fix this as Joe points out by using :CC2RESMODE: and forcing them to always display very high. This may not be a good idea for a big complicated map, but for this small map the performance difference should be minimal.

This shouldn't affect image exports, unless you export it at rather low quality, in which case the same can happen for the same reason, with the solution being the same.