ZeroTier transmisson capped to 20Mbp/s

ZeroTier seems to be capping network traffic at 20Mbp/s, even on machines that are on the same local network. Using iperf3 between machines using their local IP address, the data rate is approx 800Mbp/s, switch to the ZeroTier IP address, and it drops to 20Mbp/s. The same occurs with machines spread across the Internet, regardless of the “real” network speed, ZeroTier is always limited to 20Mbp/s. The machines are a mix of Xeon and AMD CPU’s, and the CPU load never gets high, on any core. The only thing the machines have in common are they are all running Debian 11. The mtu for the ZeroTier interface is set to 1300 across the ZeroTier network - otherwise the connections don’t work. Seems strange the data rate is capped to exactly 20Mbp/s, not 21, or 19, but 20Mbp/s, not expecting it to run at fully speed, but near to 80-90Mbp/s and to actually be different for connections between different machines. All the ZeroTier connections are direct, not relayed.
Is there a setting I’m missing in either ZeroTier or Debian, any pointers would be helpful.

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