I'm betting it is a yeast issue. Just maybe not with the yeast you are wanting to use. Do you have any set aside at room temp you could sample after time to see if anything else develops (in terms of flavor)? Or is it all kegged?
It's all kegged. Suppose I could bottle one off the keg and see. The recent particular beer is a Vienna lager with 70% Best Vienna, 23% Best Munich I, 6% Caramunich III, and a percent or so of debittered black malt. Mash was 145F for 30 minutes, 159F for 40 minutes. Boiled for 60 minutes, aerated with pure o2 for 90-120 seconds, pitched quite large slurry of 838 that was harvested less than a week before pitching.
I still feel it could be an over pitching issue but I just don't know. It just doesn't make sense to me. It certainly doesn't strike me as any sort of contamination as the beer doesn't have any strange flavors.
It doesn't seem likely to be water issue if I'm targeting amber balanced in Bru'n water with gypsum, epsom, calcium chloride, and 85% phosphoric.
I'm perplexed. Any other variables I'm missing?
One thing I've decided is I think I'm not going to push my yeast so far, only use it for a few generations then switch to a new yeast. That's more for variety than anything, but perhaps pushing a yeast too far, especially with over pitching from generation to generation is causing the yeast to perform poorly? It still attenuates well, but other than that...maybe it's compromising the beer otherwise.