Most recently these were the changes, very well documented. Nothing sounds suspicious
Changes to the CPI establishment frame (2019-2020)
Replaced Telephone Point-of-Purchase Survey (TPOPS) as source of retail establishment frame with data from the Consumer Expenditure Surveys (CE)
Eliminated redundancies and inefficiencies in survey operations and reduced household burden
Use of Quarterly Census of Employment and Wages business registry to refine the location and address data from the CE
For more on the history of the CPI and price change in the U.S see