What kind of beer did you “fix” the issue with?
If you have a water pH issue in the mash, it can be intermittent, depending on the beer you brew. Hard water will cause astringency in lighter beers unless you adjust your water. But hard water won’t cause astringency in a dark beer, because the roast malt typically is acidic enough to lower the pH.
I have only had astringency on lighter beers before I figured out my water chemistry.
