If you have or have had a white paper and you find/have found a single tiny black dot while examing the paper carefully, the paper can’t be said to be white anymore.
of this follows:
If you find one single contradiction and or fact/factor that even might contradict a presented thesis while analyzing all needed premisses that needs to be proven true in order for a thesis to be sound and to be able to present a conclusion that can be taken into consideration at the same time.
If one single needed premis for a thesis isn’t sound or even worse been proven false/wrong etc, then the thesis has fallen.
That said it doesn’t have the same sudden effect on present Paradigm.
Paradigm is a type of conclusions that always is drawn on basis of presently known "facts" and/or assumption of "facts". Remember two examples:
* Christian churches set the paradigm for our Earth in relation to stars, planets and God. To their help they used the old Greek asumptions as well as what the Fathers of the Church came up with after studying the Bible. The Fathers of the Church were humans as you and I. Thus it's understandable that the Paradigm of Earth as central point in Universe fell when Gallilei and later observations proved the Paradigm wrong.
* Theory of tectonical plates were looked on as humbug for generations. That was due to two essential factors: Assumptions re. our Earth due to religious text analyses and (of all) Darwin. When the old Paradigm fell, a new was formulated.
A Paradigm is a conclusion that a majority or a leading group of scholars in a field has presented. Whenever a Paradigm has fallen – a new Paradigm needs to replace it. (That can take some time….)