Maybe your script is not killing all instances, so try this
:kill
taskkill /F /IM chrome.exe /T
IF ERRORLEVEL 128 goto kill
Based on What are exit codes from the taskkill utility?, I'm testing for "no such process" error and repeating until we don't get that error.
Danger: this may cause an infinite loop if taskkill is failing for some reason. Tell us more context, so we can advise on other conditions to terminate the above loop. Here is a very simple basic way to stop after trying the kill command 20 times
counter=0
:kill
set /a cycles=cycles+1
taskkill /F /IM chrome.exe /T
if %cycles%==20 goto endlocal
IF ERRORLEVEL 128 goto kill
:endlocal
echo Ran taskkil %cycles% times
Let us know how it works