I had
<option name="canBeDamaged" value="true"/> <option name="canDieFromReachingMaxDamage" value="true"/> <option name="maxDamage" value="2"/>To stop the error add the following to the same unit
<option name="isConstruction" value="true"/> <option name="constructionType" value="Recruit"/> <option name="maxConstructionsPerTypePerTerr" value="1"/> <option name="constructionsPerTerrPerTypePerTurn" value="1"/>
