Oktoberfest gone bad

Hey folks, I have an issue with a recently brewed oktoberfest on which I was hoping to get some feedback. Last night my buddy and I were kegging it in preparation for our Halloween party this Saturday, and in the process decided to pull a small sample just to check the aroma/flavor. What we found was shocking to say the least...likely our worst effort to date. The aroma and flavor was that of burnt rubber - my buddy actually likened it to a pair of rubber sheets that had been urinated on, but I think that was an overstatement.

Seriously though, it did have a very strong rubbery aroma and flavor that, in our opinion, definitely ruined the beer. We certainly didn't feel comfortable serving it to friends.

In trying to retrace my steps and troubleshoot, I've searched various sources and narrowed it down to a few potential culprits: infection, poor yeast culture, or autolysis - although, you may have some other theories that I am certainly open to entertaining. Let me tell you a bit more about this one.

We brewed it using Wyeast 2206 Bavarian Lager and got a starter going about 48 hours in advance of pitching. One thing I did notice about the starter looking back on it was that it was quite sluggish and never really exhibited any strong signs of life like my ale starters do, although from what I read it seemed like this might be normal. The wort and starter were at about 52F when pitched and remained at that temp through primary fermentation. It stayed in the primary about 3 weeks and was then racked over for lagering. At that I time I took a hydro reading and it was 1.016, and didn't notice any signs of a problem at that time. I gradually lowered it to about 35F, where it remained for the next 6 weeks until last night.

Upon racking it over to the keg we noticed right away that it had a fairly strong "rubbery" aroma, and sure enough the taste was shockingly foul. At the bottom of the secondary fermenter, there was a small amount of yeast, but nothing substantial. However - and this may have been my eyes playing tricks - but it did look like a tiny bit of the yeast had an off-color, maybe even black? However, I couldn't distinguish whether or not this was some other sort of trub, but I can't even think of what that might be.

Needless to say, we were quite bummed. I would like to get some ideas about what potentially went wrong so that we can make sure this doesn't happen again.

Thanks in advance for any help!

normally autolysis isn't a real concern. I have washed and banked some yeast in the past, and some of it didn't get used quickly enough. When I pulled it out, it had turned very dark, and when i opened the mason jar it smelled unhealthy.
dead/rubbery is a decent description. almost rotten egg like but with less sulphur

i wouldn't think that the dark specs would be hops, depending on how you avoiding transfering trub to primary, so it could well be autolyzed yeast cells.

i would still let it hang for a bit...sometimes the sulphury smells of lagered beers take a while to come out of solution.