reading the same data in by two methods in RStudio gives different results from mixed in afex. One method of reading in is to Import Dataset from the Excel spreadsheet. The other is to save the Excel data as a .csv and read.csv. The former creates a tbl_df and the latter a data.frame. These give very different results when analysed by afex::mixed, though the data have the same source. Which should be trusted?
Your question unfortunately presents very little detail to understand what the actual problem is. I would guess it has something to do with the data types of the variables passed to mixed. Like most R modeling functions it behaves differently for factors versus numerical variables. You can check the type of your data with str(), e.g., str(my_data).