Sorry to hear you sent them both back. Unless you are extremely cold natured, there is always a chance of not getting the temperature right when away from home. Hotels and cruise ships - large blocks of individually adjusted air conditioning - just seems to present problems.
As for having the room steward magically adjust your temperature, the controls are all pretty straight forward. Maybe no numbers, but if you are hot, dial it down.
Our May cruise, we left it on the coldest setting, kept the curtains drawn in the daytime (oceanview), but it took nearly 5 days to finally be cool enough for my sister (and she did have a fan). In the meantime, I wore a polar fleece jacket over long pajamas. Two people, same cabin - different experience.
Hot air rises - the upper berth may be warmer than the bed.
If I am correct, other than the Magic & Wonder, the power turns off when you take the card from the control slot as you leave. Which would mean your room has no cool or circulating air in the Caribbean. In a metal box of a cabin. And often, people leave the darkening curtain open.
Just some thoughts.