Thanks for writing in, we're happy to take a look into these issues! It sounds like a point of contention here is the difference between the apparent graphical behavior (wheel sinking into object) and the actual physics simulation. Every object in ANVEL is represented by 3D art assets and also physical dimensions; the two don't necessarily have to line up exactly (check out http://wiki.anvelsim.com/3/index.php/Object_Definition_Overview for more info). In this case, it looks like the Hay Bale asset was constructed with a bounding box with reasonable x and y dimensions, but the z dimension is a little too short. Fortunately, objects can be easily edited. If you open up BarrierDefinitions.xml in the resources/Objects directory of the ANVEL install dir, you can modify the Hay Bale like so:
<object name="Hay Bale" category="Objects/Barriers" tags="ANVEL_Common">
<ogre3d mesh="hay_bale.mesh" shadows="on" zUp="true" maxRenderDistance="700.0">
<position x="0.0" y="0.0" z="-0.335"/>
<shape type="box" x="1.5" y="0.9" z="0.67"/>
Which will change the bounding box and lead to behavior like this:
Note that enabling the "Debug" checkbox in the World View window will show/hide the bounding boxes so you can visualize the collisions between the wheel and the object more easily. Unchecking the "Geometry" toggle will hide the visual aspect of the simulation entirely.
With regards to the instability of the Coroware vehicle while trying to climb obstacles - I am able to reproduce the issue in some cases, so we'll go ahead and take a look at what could be causing the instability. You may want to experiment with the P3-AT vehicle for the time being, which is in the same small UGV class as the Coroware but lacks the suspension rocker arms that seems to be causing some trouble.
Hope this information helps you in your investigations!