"Is there some mechanism to ensure that the churches understands correctly the apporpiate teachings of the scripture with in the context of their day?"
~ Sure, I understand now. We certainly don't say that preachers preach infallably (unless you're the pope in the RCC- they beleive he can, at times, speak infallably). Ministers are capable, and do err. No question there. So, we try to draw on as many resources as possible to ensure as much adherence to truth as we can. This is why the pubic preaching of the Word is so seriously important. One great resource we have is called historical consensus. If we can find where the church as generally agreed on a matter down through history, that goes a long way in helping ensure we're not teaching anything abberant or completely new to NT doctrine. Along those same lines, you'll find where the church has most definitely disagreed on many matters, but even in those cases it is still benefical to see how certain controveries and the like have been handled historically.
I hope this helps.