Roger that, Dantoo.
I checked out the terrain last night... the problem with A4 is that the small field with the single diagonal runway was turned 45°, so that the runway faces N-S. Since a diagonal runway is much longer than the runways on the N-S/E-W axes (1.41414 longer if you remember your trig) the runway overruns the edge of the tile and carries into the next tile, which is a forest tile.
If A4 must be used, spawn at the hangar, and don't plan on using the rearm pads there.
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The problem with A30 "rearm bug" is a bit more subtle... essentially, the taxiway runs right alongside the adjacent tile, which is on a slope. If you wander onto that slope, it is just steep enough that it will dip your wings into the ground, at least with an LA5 it will, and cause damage.
Since this is not really a bug, the only way to avoid this is to use proper taxiing techniques, and stay on the taxiway.