Overpowering yeasty flavor after kegging

So after a week or two in the keg my beer develops an almost unnaturally strong flavor. It is a estor or phenolic flavor I would expect from yeast, but it is so strong all other flavors disappear. I can hardly recognize my beers once this happens.

I need help troubleshooting here..

-some variables to this flavor developing:

-I may have correlated this to happening when I warm up my Keezer. I also use this to ferment lagers so I will regularly warm from 35 up to mid 50's during the primary. I am going to stop brewing lagers to see if this is the culprit. I do attemp to compensate with increaseing the regulator pressure to maintain constant carb levels. I shoot for 1.9

- I sanitize with bleach. I'm not sure this could be it due to delay in flavor development. Also I use bleach to sanitize car boys and other equipment so why would it not be present right away? I always rinse a minimum of 3 times and make sure the bleach smell is no longer present. I suppose I could start using one step.

-line contaminate. Well it seems present even past first poor. But perhaps it back contaminates all the way to the keg?

What else could I try to eliminate the flavor culprit?

Split a batch in half. Bottle half and keg the other half. Determine if the off flavor is in both the keg and bottle or just one. If it's in the keg side, there's your problem. If it's in both then I'd start at the beginning.