Steps to reproduce:

• Create a "Simple check" item with a icmppingsec key.
• Set the sever DebugLevel to 4
• Observe the fping command generated by Zabbix.
• Observe the recorded ping times.
• Repeat with a version of Zabbix (eg 3.4) that does not use a "-i0" option with fping.

Result:

The fping commands generated by Zabbix-6.2 include a "-i0" option.  The documentation for simple-check/icmppingsec acknowledges  this: "Zabbix tries to detect the minimal value in milliseconds that fping allows to use with -i by trying 3 values: 0, 1 and 10. The value that first succeeds is then used for subsequent ICMP checks."

However at my site, although the  i0 option "works", it results in ping times that are much slower than a larger -i value (eg, fping's default value of 10.)  Zabbix-3.4 did not use the i option.  Consequently I am seeing ping times much greater and with much larger variance then previously. 

Running both Zabbbix 3.4 and Zabbix 6.2 for an hour, each with an identical set of 7 icmpingsec items (update interval=15s) gives the following results for one of the addresses:

Ping response times in mS:

I can reproduce similar results running fping by hand, with and without a "-i0" option.

I do not understand why this is happening (the internal workings of fping or the upstream network characteristics that may be contributing) but since it is happening, I believe Zabbix needs to provide some means for the user to control at least the minimal value used with the -i option given to fping.