OpenVPN client throttled no qos active

Hello,

we have a customer here with an Openvpn client active. We have 20 MBit/s Upload but he only gets 3 MBit/s (400 Kbit/s). No QoS or Throttling is active but it seems the UTM is throttling this traffic. He tried with his LTE onboard and has 8 MBit/s upload. So it must be our UTM throttling this traffic.

Any ideas?

Thx

Björn