Goodie hut respawn chance

Trying to create a goodie hut that spawns a monster every other turn. Set "<RespawnChance>" to 100, and "<Respawndelay>" to 1. After 5 turns during a test, nothing spawns.

Example: This is from the bottom of "Lair_ButchermanHecatomb_Final" in CoreGoodieHuts.xml

<Encounter>
<Liklihood>-1</Liklihood>
<WillRespawn>1</WillRespawn>
<RespawnChance>5</RespawnChance>
<RespawnDelay>7</RespawnDelay>
<WanderingRadius>5</WanderingRadius>
<UnitInstance>
<UnitType>Butcherman_Martyr</UnitType>
<Level>4</Level>
</UnitInstance>
<UnitInstance>
<UnitType>CorpseSpider</UnitType>
<Level>5</Level>
</UnitInstance>
<UnitInstance>
<UnitType>Butcherman</UnitType>
<UnitGroupingType>UnitGroupingType_Party</UnitGroupingType>
<Level>3</Level>
</UnitInstance>
<UnitInstance>
<UnitType>Butcherman</UnitType>
<Level>3</Level>
</UnitInstance>
</Encounter>

I have seen this goodie hut spawn this unit twice in one game, and only about 10 turns between. Seems like the chance must be higher than 5% right?

Is the "Respawn chance" out of a denominator other than 100? Is there another factor or limitation at work in the code?