Zabbix-agent2, system.run and docker issue "docker.sock: connect: permission denied"

[Kirill42]

My details:
Zabbix server 5.2.3 (docker-compose installation)
zabbix-agent2 5.0.9-1+buster (from PPA)

Config /etc/zabbix/zabbix_agent2.conf contains:
AllowKey=system.run[*]

Permissions for zabbix user on host:
# id zabbix
uid=106(zabbix) gid=998(docker) groups=998(docker)

su - zabbix -s /bin/bash
$ docker info
Client:
Context: default
Debug Mode: false
Plugins:
app: Docker App (Docker Inc., v0.9.1-beta3)
...

For example I'm trying run speedtest
system.run[docker run --rm pschmitt/speedtest --server-id=17137 --progress=no | grep -oP "Download:\s+\K\w+"]

Output from Zabbix Server GUI:

Value of type "string" is not suitable for value type "Numeric (unsigned)". Value "docker: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Post http://%2Fvar%2Frun%2Fdocker.sock/v1.24/containers/create: dial unix /var/run/docker.sock: connect: permission denied.
See 'docker run --help'."

Debug log:

2021/03/16 13:24:59.000426 executing exporter task for itemid:76499 key 'system.run[docker run --rm pschmitt/speedtest --server-id=17137 --progress=no | grep -oP "Download:\s+\K\w+"]'
2021/03/16 13:24:59.000448 [SystemRun] Executing command:'docker run --rm pschmitt/speedtest --server-id=17137 --progress=no | grep -oP "Download:\s+\K\w+"'
2021/03/16 13:24:59.044991 [SystemRun] command:'docker run --rm pschmitt/speedtest --server-id=17137 --progress=no | grep -oP "Download:\s+\K\w+"' length:262 output:'docker: Got permissi'
2021/03/16 13:24:59.045035 executed exporter task for itemid:76499 key 'system.run[docker run --rm pschmitt/speedtest --server-id=17137 --progress=no | grep -oP "Download:\s+\K\w+"]'

From shell:

zabbix@vhost:~$ docker run --rm pschmitt/speedtest --server-id=17137 --progress=no | grep -oP "Download:\s+\K\w+"
94

I restarted the agent and docker, it didn’t work. What could be the reason?