I figured it would be a good idea to collate all the known bugs for the AH terrain, object and weather editors into one thread. While this might be more on topic in the bugs forum it is more likely to get read by those who would find it useful in the terrain forum.
Here's a few I've discovered by experience, searching, or by help received from NHawk and others in this forum. Please add any more you can think of.
A manned 37mm placed onto a terrain using the bas0 shape in the TE will not work properly. Although it can be destroyed like any other AA in the game, it does not APPEAR to be destroyed. You still see an intact 37mm in the game, even though it is actually knocked out.
River deltas are not visible in the game or the TE. There is a fix available at
Mr Midi's Place but using this would count as a custom object which is not allowed for an MA terrain.
The base texture for the shore battery hill is terr0006 in the TE, but is terr0106 in the game.
Saving your terrain in the TE can sometimes cause field and strat icons to rearrange themselves on the map. You have to right click them off and on again so they appear in their correct locations.
A map generated by the TE can have beaches applied to the coastlines that appear one square out of alignment. Sometimes the beaches are not generated at all.