How to reproduce:

• set up an action with remote command to be run on Zabbix agent,
• set action target to "Host" AND "Current host"
  Remote command will run twice on target host.
  Other cases:
• set action target to "Host" AND "Current host" AND "Host group" (where host is member of).
  Again, remote command will run twice on target host.
• set action target to "Current host" AND "Host group" (where host is member of).
  Again, remote command will run twice on target host.

If a host is targeted as "Host" and "Host group" at the same time, it results in script execution one time.
Targeting "Current host" results in "independent" execution on script.