Ok, that's a red flag. 7 hours is a long time in a mash tun. And it occurred to me: what are you using to heat up your mash?
You're moving right through temperature that lactobacillus likes at a very slow speed without yeast competing for food and nutrients. This is giving the lactobacillus a head start.
It's really difficult to diagnose this from a computer without seeing and tasting your setup. It could be anything from improperly rinsing out your condenser and leaving chemical in the thing, leading to an off flavor......to what I mentioned before: acrolein (which could be described as band aid/phenolic) from lactobacillus. Acrolein can stick to the inside of your still, ruining batches until all internal surfaces come into contact with the cleaning chemical, and are then rinsed.
My advice, for multiple reasons: try cutting your grain bill by 1/3rd. To me, this sounds like the most likely culprit. This will greatly thin the mash, accelerating both heating and cooling, as well as facilitating a quicker fermentation as the yeast has far less sugar to eat, leaving nothing for the lactobacillus. Target a 12 Plato mash. Do you know how to do that? Fight to get in and out of the mash tun as quickly as possible. And then after 72 hours, get that mash into the still.
If the problem goes away, then you know that the issue is your mashing protocol. It's also easier to get a far higher lactobacillus count in milled grain. You're basically exposing all that starch and things like lignocellulose to the bacteria, and then putting it in a warm sack...whereas whole grains have an endosperm protecting it from harm until moments before mashing.