First off - you need to remove ALL the old finish. What you have there is a chemical soup that has reliquified. You need to sand down to raw wood.

Secondly you need to deal with the crawlspace. Just because it 'looks' dry doesn't mean it is. The ground is sitting on the biggest swimming pool in our solar system (Earth from space = water planet). The 'dry' earth is evaporating off water at an astounding rate.

Many old A/C units to NOT have the power to keep the home around 40% humidity. The temperature (80's is high...85 deg is the top edge of 'indoor living conditions' for human habitation). is almost irrelevant (although warm air holds MORE humidity than cold air). See if you can drop the temp down to 72 F and the humidity BELOW 50% and see where that gets you. And yes...that is an expensive experiment...but it needs to be done. You need to dry out that wood.

Remember: carpet holds moisture. Carpet PAD holds moisture. Carpet pad CAN have a chemical reaction to old wood finishes. Not always...but it can happen. So you have wet pad (way too much humidity in a home sitting over open/moist dirt) with moist carpet sitting over wood that is soaking up moisture from the crawl space causing the old finish to liquify.

I would be prepared to remove the soaked planks. The age of the home will dictate whether or not they can be patched or if they should be removed completely.