I was curious if there were examples or instances where one generation of Rabbis established an interpretation of the law which was followed accordingly, only to have another generation of Rabbis lawfully reverse the previous decision entirely.
In Berachot 23a the Sanhedrin ruled that tefillin must not be brought in a bathroom. So people would leave them outside. But they frequently got stolen. So the Sanhedrin reversed its ruling.
Tevilas Ezra is one that comes to mind.
Avoda Zara 35b says:
ואלו דברים של עובדי כוכבים אסורין ואין איסורן איסור הנאה חלב שחלבו עובד כוכבים ואין ישראל רואהו והפת והשמן שלהן. רבי ובית דינו התירו השמן
there was a Decree not to drink/eat milk that a Goy milked without being seen by a Jew, and not to eat Bread and oil of the Goyim. Rebbi (Rabbi Yehuda Nesia see Rashi) and his Beis din permitted the oil made by a Goy (even though it was initially forbidden to eat).