If you set interval for web monitoring to 1 seconds, sometimes values for some timestamps are missing. Problem occurred on test VM with low load (load average: 0.04, 0.04, 0.05), Zabbix server was configured to minimum (without trappers, pollers, discoverers, ...., only with 2 httppollers), webmonitoring had only one scenario with one step for check of static content from local VM.

1.) case 193806
values for 2 seconds are missing - log from server (debug level4) for time 19380* is attached

2.) case 201524
value for 1 second is missing - log from server (debug level4) for time 20152* is attached

SQL script for detection of missing values is attached, output for last ~2 hours for item Response time is attached. Related values to Response time (Download speed for step/scenario) are missing also in the same times.