Filmstrip and Performance Summary metrics do not match

Web Performance Discuss Test Results
1

Hello everyone,
I’ve noticed that many of the tests I executed have different values (with differences higher than 100ms) if we compare FCP/LCP values presented on the Performance Summary with the FCP/LCP moments displayed on the filmstrip.

You can use this test result as an example. The LCP displayed on the summary is 3.448, while on the filmstrip, we can see the LCP element being displayed at 3.201.

Maybe this is more frequently, or only seen, in multi-stepped (tests with WPT scripts that navigates through different pages) tests…not sure.

My WPT script is the following one:

logData	0
setEventName	Visit PLP
navigate	https://www.amiparis.com/en-gb/collections/men-shirts
setEventName	Click on ACCEPT ALL GDPR Button
execAndWait	document.getElementById("didomi-notice-agree-button").click()
setEventName	Visit Home
clearCache
logData	1
navigate	https://www.amiparis.com/en-gb

Any clue why this discrepancy exists, and/or which data is more accurate (test summary data or filmstrip)?

Thanks in advance!