Oily after Taste

[CoppertopTinMan]

Hello,

I have finished up my second generation of UJSSM and during my spirit run the whiskey developed an oily after taste. It is identical in taste to the rest of the hearts, but it has a clingy mouthy feel from some sort of ester. It still has a high average ABV (75%) so I am hesitant to call it tails, and when I got further down the line around 55% ABV it seems to disappear and the taste transforms into what I normally would call tails. It is not cloudy or any other discoloration so I also don't believe it to be puke. I know I can run it again, but I was wondering if anyone has experienced this and if carbon would remove the oil? Does anyone have an idea of the cause?

Here is my process:

This is a 10 gal wash with about 25% backset from the first gen. Ran on a keg pot still, that is electrically heated and controlled by a PID. Probably this still 15th run and it was cleaned thoroughly and used for a stripping run the night before with no issues.

Filled the keg with around 4 gallons from my first gen and second gen striping runs combined. ABV was around 50%
I added a gallon of spring water to lower the ABV and make sure I had enough liquid to be above my element.

It ran at 170 degrees for 300ml to remove foreshots and then began collecting heads.

When it tasted clean and burned blue I bumped up the heat to 174 and collected around 1200 ML of hearts. ABV of 80%

After around 1200ml the oil appeared and continued for around a half gallon while stepping down in ABV. It was separated in 300ML jars, but I mixed all the jars with oil and it averaged a 75% ABV.

After the half gallon I got the wet cardboard taste and entered "tails", so I turned up the heat to 185 and stipped down to 30% ABV for feints run later. While in tails I tasted it, and while the flavor was crappy the oily taste was gone.

When I emptied the keg the wash was cloudy, but didn't appear to have discoloration or scorching.