Not sure if this is possible, but perhaps your descriptor of burnt rubber is really a sulfur-based smell (like maybe a burnt match)? One way for you to aromatically test that is to take some very light lager and treat it with some sodium metabisulfite and compare the two, adding more and more of the Sodium Metabisulfite to the light lager until it approximates your beer's aroma, if at all. This condition is typically from a stressed yeast condition (low pitch rate, too high of fermentation temperature, as well as bacterial infection).
Good luck. I hope it dissipates with time.