There are no instances in the Gemorah of Chazal being wrong. Period.
So, when one Tanna disproves the statements of another Tanna, is not the latter Tanna wrong (eilu v’eilu aside)?
It is indisputable that what they say is from a divine source. Period. You cannot dispute the word of Chazal. Period.
How is that indisputable? Chazal themselves held that it was possible for them to be wrong — see the dispute regarding where the sun goes at night.
The Wolf