Your post is similar to mine here: Response Times in Log Files, Key Press vs. Release, and EXP log messages
If I resolve my question on that post, I think you will also find what you are looking for and I’ll follow up.
I actually did find a great match between log file and csv, but assuming that the EXP is logged on the next frame flip approximately, and that assumption is very much under debate. See my post.
I have some questions for you that will help the investigation:
(1) Where do you call Dist6_post_9: autoDraw = true?
(2) Are all of your RT’s computed from the log files just small underestimates of the .csv RT?
Also note that post that was unanswered was not online psychopy, so the coding will be different probably.