Question

Hello!
If a person has accepted a certain rabbi upon himself, and let’s assume the validity of that acceptance takes effect simply by the acceptance itself (as with our acceptance of the authority of the Babylonian Talmud, or like a community that accepts a rabbi upon itself). The meaning of this would be that that person must rule like the rabbi in everything.
If after some time that same person studies and reaches a different conclusion regarding the laws of the Sabbath, for example, does that prevent him from accepting that rabbi’s words in other areas of Jewish law?
For example: until now I have ruled like a certain rabbi in a place where I know there are many other different halakhic opinions. But now, after I ruled Jewish law differently in another case, and as a result my acceptance has been nullified — can I still rule like that rabbi, or do I now need to act according to the rules of doubt?
I hope I explained myself properly!
Thank you very much