Negative user reaction to redesigned product

Hope you're all healthy and safe. A redesigned version of a product is recently launched and we've been hearing negative reviews. In order to redesign the product, we followed a thorough process; investigate the existing version with users (user testing, tree testing, etc), detect issues, review literature & best practices, drive insights and set principles, apply them to new design concept and test it with user again to ensure the acceptance of the concept. The results were promising and the concept was approved. So, the development started...

There could be many reasons for these negative reactions such as no ability to reflect all the concepts at the first product launch due to technical matters or last-minute business changes that could violate the consistency or compensations on design during development... However, I would like to ask if you have had any experience such, a product launch facing resistance, or do you know any case studies or academic backup for this situation.