ive gone through the same thing. nothing consistently happening, but it happened to me with 3 batches i did.
i always said, "How can it be infected? I did everything right." My problem was with a Baltic Porter, a Pilsen IPA (Pilsner hop-fortified, dryhopped, woodchipped, and fermented with Ale Yeast), and a Tripel, with 3 different results.
1. Baltic Porter- high alcohol content, long sitting beer. once i bottled it, it was a geyser beer. tasted very good, something slightly weird about it, but i thought it just had to do with my flavor profile, alcohol content, extended aging, etc etc. now it's 6-7 months later and even fridged for a month i have to open it over a sink. bubbles are too fine, leads me to believe something got in there and is not dying with the high alcohol content. I have 1 left...not sure when it will be drunk but oh it will be, (probably) infected and all...
2. Pilsen IPA- after about 7 weeks this beer began foaming like crazy when it was opened. quite offensive since you couldn't really drink it without a mouthful of foam. i let it sit another month. then i fridged it for a week. opened one up over the sink, boom, great beer, no foamover. no signs of carbonation issues, just a perfect beer (and to think i was ready to give up on this). i took it to my homebrew meeting later that next month and it was a hit, even among the skilled vets. patience may be a virtue on your cascadian, but it may not be.
3. Tripel- Made it in October. After 5-6 months it was amazing. Then all of a sudden it began gushing. WTF? Don't tell me this perfect beer is about to turn?! 1 month later, that subsided, and it's back to the best beer.
Hopefully my case studies will give you hope. 2 out of 3 isn't bad. I'm very crazy on my sanitation etc though so it leaves me nervous, but I think it's more than i can personally understand.
While i'm saying it, can anyone vouch that this has happened to them with similar positive results? I'm convinced it's the long aging and the way the yeast reacts to the corn sugar, but I can't be 100%