The oil turned black after being distilled in the tower. What’s the reason? How to break it?

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Our tower is used to remove fatty acids from oils. But a few days ago, the factory experienced a sudden power outage, which caused the vacuum level to drop; meanwhile, the temperature inside the tower was between 250 and 260 degrees. The oil inside has oxidized. The oil that comes out of the tower when it is started up again will be black. I asked some people from the factory before; this situation had occurred before as well, but after turning it on for about 2 hours, the color returned to normal. It has been 48 hours since we started using it this time; the color has improved, but it remains dark. If our oil turns black, there are mainly two possible reasons: 1) Resins remaining in the oil have not been completely removed, and they carbonize at high temperatures, causing the oil to turn black ； 2. Oxidation: Insufficient sealing of the tower allows air to enter it, causing the oil inside to oxidize and turn black. However, our tower’s seal integrity was checked before it was put into use, the oil fed into the tower was also inspected, and the degumming process worked properly. What exactly is causing the oil coming out of our tower to be so dark? Are there any other reasons? Also, if the tower needs to be cleaned, what method is better to use? Option 1: Steam purging ； Option 2: Keep circulating oil, with the temperature around 250–260 ； Option three: use an 8% alkaline solution for soaking for 3 days, with the temperature maintained at 60–80°C. If any friends are familiar with this industry or have encountered such a situation, I would be grateful if you could share your insights. Thank you in advance!