Judging by your spirits and your comment you know a lot about fermentation and spirits production as a whole. I have one adjustment to the statement above though.
"The solution for this is called Dunder, which is the same as Sour Mash in Whiskey."
In my opinion "sour mash" outside of whiskey production is usually referred to as backset cycle and Dunder is the gloop you get from an intentional bacterial infection in backset usually in a pit or tank. For details check out this link. https://cocktailwonk.com/2016/03/days-of-dunder-setting-the-record-straight-on-jamaican-rums-mystery-ingredient.html
If you really want to geek out follow the link through to Boston Apothecary...
Not trying to offend, trying to help. The reason I care is they have very different effects.