Check (or uncheck) isTrials
When you define a loop, pay attention to the Is trials option.
If isTrials is checked then the data file will have a separate row for each iteration of the loop. Programmatically, the command thisExp.nextEntry() is processed at the end of each iteration of the loop.
If isTrials is unchecked then any data saved during the loop will replace existing data rather than appearing on the next row. If you accidentally uncheck it you will therefore only get data from your final trial and will need to process the log files if you want to recover lost data. Online, this was implemented in 2022.2.0.
If you want to choose when data is saved to a new row then isTrials should be unchecked and thisExp.nextEntry() should be added accordingly.