A network hierarchy implementation with mininet get packets lost unexpectedly.

When all hosts are running, I connect to all of them manually and run iPerf3 unidirectional tests from clients to server host. So all traffic is going from clients to the server via s1 host.

"ip -s l"-result form s1 node:

Packets received by the S1: 858_490+860_126+858_833+860_410+431_645 = 3_869_504
Packets sent from S1 to the server: 423_576
The difference = 3_869_504 - 423_576 = 3_445_928
According to the calculation 3_445_928 packets were unexpectedly lost.

Network is created with: net = Mininet(controller=OVSController, link=TCLink)
All links were created with thos args: net.addLink(host, switch, delay=f"5ms", bw=10000, limit=2000000)

All iperf3 clients had 1G bandwidth limit on UDP traffic.
Pure iperf3(no namespaces or mininet) produces 56Gbit/s.

mn --version : 2.3.0